Mobile gas and chemical imaging camera

ABSTRACT

In one embodiment, an infrared (IR) imaging system for determining a concentration of a target species in an object is disclosed. The imaging system can include an optical system including an optical focal plane array (FPA) unit. The optical system can have components defining at least two optical channels thereof, said at least two optical channels being spatially and spectrally different from one another. Each of the at least two optical channels can be positioned to transfer IR radiation incident on the optical system towards the optical FPA. The system can include a processing unit containing a processor that can be configured to acquire multispectral optical data representing said target species from the IR radiation received at the optical FPA. Said optical system and said processing unit can be contained together in a data acquisition and processing module configured to be worn or carried by a person.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/700,791, filed Apr. 30, 2015, entitled “MOBILE GAS AND CHEMICALIMAGING CAMERA,” which claims priority to U.S. Provisional PatentApplication No. 61/986,885, filed May 1, 2014, entitled “MINIATURE GASAND CHEMICAL IMAGING CAMERA;” U.S. Provisional Patent Application No.62/012,078, filed Jun. 13, 2014, entitled “MINIATURE GAS AND CHEMICALIMAGING CAMERA;” U.S. Provisional Patent Application No. 62/054,894,filed Sep. 24, 2014, entitled “MOBILE GAS AND CHEMICAL IMAGING CAMERA;”U.S. Provisional Patent Application No. 62/055,342, filed Sep. 25, 2014,entitled “MOBILE GAS AND CHEMICAL IMAGING CAMERA;” U.S. ProvisionalPatent Application No. 62/055,549, filed Sep. 25, 2014, entitled “MOBILEGAS AND CHEMICAL IMAGING CAMERA;” and U.S. Provisional PatentApplication No. 62/082,613, filed Nov. 20, 2014, entitled “MOBILE GASAND CHEMICAL IMAGING CAMERA,” the contents of each of which is herebyincorporated by reference herein in their entirety and for all purposes.U.S. patent application Ser. No. 14/700,791 also claims priority to U.S.Provisional Patent Application No. 61/986,886, filed May 1, 2014,entitled “DUAL BAND DIVIDED APERTURE INFRARED SPECTRAL IMAGER (DAISI)FOR CHEMICAL DETECTION;” U.S. Provisional Patent Application No.62/082,594, filed Nov. 20, 2014, entitled “DUAL-BAND DIVIDED-APERTUREINFRA-RED SPECTRAL IMAGING SYSTEM;” U.S. Provisional Patent ApplicationNo. 62/021,636, filed Jul. 7, 2014, entitled “GAS LEAK EMISSIONQUANTIFICATION WITH A GAS CLOUD IMAGER;” U.S. Provisional PatentApplication No. 62/021,907, filed Jul. 8, 2014, entitled “GAS LEAKEMISSION QUANTIFICATION WITH A GAS CLOUD IMAGER;” and U.S. ProvisionalPatent Application No. 62/083,131, filed Nov. 21, 2014, entitled “GASLEAK EMISSION QUANTIFICATION WITH A GAS CLOUD IMAGER,” the contents ofeach of which is hereby incorporated by reference herein in theirentirety and for all purposes.

TECHNICAL FIELD Field of the Invention

The present invention generally relates to a system and method for gascloud detection and, in particular, to a system and method of detectingspectral signatures of chemical compositions in infrared spectralregions.

Description of the Related Technology

Spectral imaging systems and methods have applications in a variety offields. Spectral imaging systems and methods obtain a spectral image ofa scene in one or more regions of the electromagnetic spectrum to detectphenomena, identify material compositions or characterize processes. Thespectral image of the scene can be represented as a three-dimensionaldata cube where two axes of the cube represent two spatial dimensions ofthe scene and a third axis of the data cube represents spectralinformation of the scene in different wavelength regions. The data cubecan be processed using mathematical methods to obtain information aboutthe scene. Some of the existing spectral imaging systems generate thedata cube by scanning the scene in the spatial domain (e.g., by moving aslit across the horizontal dimensions of the scene) and/or spectraldomain (e.g., by scanning a wavelength dispersive element to obtainimages of the scene in different spectral regions). Such scanningapproaches acquire only a portion of the full data cube at a time. Theseportions of the full data cube are stored and then later processed togenerate a full data cube.

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

In one embodiment, an infrared (IR) imaging system for determining aconcentration of a target species in an object is disclosed. The imagingsystem can include an optical system including an optical focal planearray (FPA) unit. The optical system can have components defining atleast two optical channels thereof, said at least two optical channelsbeing spatially and spectrally different from one another. Each of theat least two optical channels can be positioned to transfer IR radiationincident on the optical system towards the optical FPA. The system caninclude a processing unit containing a processor that can be configuredto acquire multispectral optical data representing said target speciesfrom the IR radiation received at the optical FPA. Said optical systemand said processing unit can be contained together in a data acquisitionand processing module configured to be worn or carried by a person.

In another embodiment, an infrared (IR) imaging system for determining aconcentration of a target species in an object is disclosed. The imagingsystem can comprise an optical system including an optical focal planearray (FPA) unit. The optical system can have components defining atleast two optical channels thereof, said at least two optical channelsbeing spatially and spectrally different from one another. Each of theat least two optical channels can be positioned to transfer IR radiationincident on the optical system towards the optical FPA. The system caninclude a processing unit containing a processor that can be configuredto acquire multispectral optical data representing said target speciesfrom the IR radiation received at the optical FPA. Said data acquisitionand processing module can have dimensions less than 8 inches×6 inches×6inches.

In another embodiment, an infrared (IR) imaging system for determining aconcentration of a target species in an object is disclosed. The imagingsystem can include an optical system including an optical focal planearray (FPA) unit. The optical system can have components defining atleast two optical channels thereof, said at least two optical channelsbeing spatially and spectrally different from one another. Each of theat least two optical channels can be positioned to transfer IR radiationincident on the optical system towards the optical FPA. The system caninclude a processing unit containing a processor that can be configuredto acquire multispectral optical data representing said target speciesfrom the IR radiation received at the optical FPA. Said data acquisitionand processing module can have a volume of less than 300 cubic inches.

In yet another embodiment, a method of identifying a target species orquantifying or characterizing a parameter of the target species in anobject is disclosed. The method can include wearing or carrying a dataacquisition and processing module. The data acquisition and processingmodule can comprise an optical system and a processing unit incommunication with the optical system, the optical system including anoptical focal plane array (FPA) unit. The method can include capturingmultispectral infrared (IR) image data at the FPA unit from at least twooptical channels that are spatially and spectrally different from oneanother. The method can include acquiring multispectral optical datarepresenting the target species from the IR radiation received at theFPA.

In another embodiment, a system for monitoring the presence of one ormore target gases at one or more installation sites is disclosed. Thesystem can include a plurality of infrared (IR) imaging systems, eachimaging system comprising a data acquisition and processing module. Thedata acquisition and processing module can be configured to captureinfrared images of the one or more target gases in real-time. The dataacquisition and processing module can be configured to associate eachcaptured infrared image with a location at which the one or more targetgases are present. The data acquisition and processing module can beconfigured to transmit image data associated with the one or more targetgases and location data associated with the location of the one or moretarget gases to a central server.

In yet another embodiment, a method for monitoring the presence of oneor more target gases at one or more installation sites is disclosed. Themethod can comprise receiving image data from a plurality of IR imagingsystems located at a plurality of installation sites and configured tobe worn or carried by a person. Each IR imaging system can be configuredto capture infrared images of the one or more target gases in real-timeand to associate each captured infrared image with a location at whichthe one or more target gases are present. The method can includeprocessing the received image data to identify the installation sites atwhich the one or more target gases is detected.

Details of one or more implementations of the subject matter describedin this disclosure are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings and the claims. Note thatthe relative dimensions of the following figures may not be drawn toscale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of an imaging system including a common frontobjective lens that has a pupil divided spectrally and re-imaged with aplurality of lenses onto an infrared FPA.

FIG. 2 shows an embodiment with a divided front objective lens and anarray of infrared sensing FPAs.

FIG. 3A represents an embodiment employing an array of front objectivelenses operably matched with the re-imaging lens array. FIG. 3Billustrates a two-dimensional array of optical components correspondingto the embodiment of FIG. 3A.

FIG. 4 is a diagram of the embodiment employing an array of fieldreferences (e.g., field stops that can be used as references forcalibration) and an array of respectively corresponding relay lenses.

FIG. 5A is a diagram of a 4-by-3 pupil array comprising circular opticalfilters (and IR blocking material between the optical filters) used tospectrally divide an optical wavefront imaged with an embodiment of thesystem.

FIG. 5B is a diagram of a 4-by-3 pupil array comprising rectangularoptical filters (and IR blocking material between the optical filters)used to spectrally divide an optical wavefront imaged with an embodimentof the system.

FIG. 6A depicts theoretical plots of transmission characteristics of acombination of band-pass filters used with an embodiment of the system.

FIG. 6B depicts theoretical plots of transmission characteristics of aspectrally multiplexed notch-pass filter combination used in anembodiment of the system.

FIG. 6C shows theoretical plots of transmission characteristics ofspectrally multiplexed long-pass filter combination used in anembodiment of the system.

FIG. 6D shows theoretical plots of transmission characteristics ofspectrally multiplexed short-pass filter combination used in anembodiment of the system.

FIG. 7 is a set of video-frames illustrating operability of anembodiment of the system used for gas detection.

FIGS. 8A and 8B are plots (on axes of wavelength in microns versus theobject temperature in Celsius representing effective optical intensityof the object) illustrating results of dynamic calibration of anembodiment of the system.

FIGS. 9A and 9B illustrate a cross-sectional view of differentembodiments of an imaging system comprising an arrangement of referencesources and mirrors that can be used for dynamic calibration.

FIGS. 10A-10C illustrate a plan view of different embodiments of animaging system comprising an arrangement of reference sources andmirrors that can be used for dynamic calibration.

FIG. 11A is a schematic diagram illustrating a mobile infrared imagingsystem configured to be carried or worn by a human user.

FIG. 11B is a schematic diagram illustrating an installation site thatcan be monitored by multiple infrared imaging systems.

FIG. 12 is a schematic system block diagram showing a mobile infraredimaging system, according to one embodiment.

FIG. 13A is a schematic system diagram of an optical system configuredto be used in the mobile infrared imaging systems disclosed herein,according to various embodiments.

FIG. 13B is a schematic system diagram of an optical system configuredto be used in the mobile infrared imaging systems disclosed herein,according to other embodiments.

FIG. 14A is a schematic perspective view of a mobile infrared imagingsystem mounted to a helmet, according to various embodiments.

FIG. 14B is an enlarged schematic perspective view of the mobileinfrared imaging system shown in FIG. 14A.

FIG. 14C is a perspective cross-sectional view of the mobile infraredimaging system shown in FIGS. 14A-14B.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION I. Overview of Various Embodiments

The following description is directed to certain implementations for thepurposes of describing the innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice, apparatus, or system that can be configured to operate as animaging system such as in an infra-red imaging system. The methods andsystems described herein can be included in or associated with a varietyof devices such as, but not limited to devices used for visible andinfrared spectroscopy, multispectral and hyperspectral imaging devicesused in oil and gas exploration, refining, and transportation,agriculture, remote sensing, defense and homeland security,surveillance, astronomy, environmental monitoring, etc. The methods andsystems described herein have applications in a variety of fieldsincluding but not limited to agriculture, biology, physics, chemistry,defense and homeland security, environment, oil and gas industry, etc.The teachings are not intended to be limited to the implementationsdepicted solely in the Figures, but instead have wide applicability aswill be readily apparent to one having ordinary skill in the art.

The spectral image of the scene can be represented as athree-dimensional data cube where two axes of the cube represent twospatial dimensions of the scene and a third axes of the data cuberepresents spectral information of the scene in different wavelengthregions. The data cube can be processed using mathematical methods toobtain information about the scene. Some of the existing spectralimaging systems generate the data cube by scanning the scene in thespatial domain (e.g., by moving a slit across the horizontal andvertical dimensions of the scene) and/or spectral domain. Such scanningapproaches acquire only a portion of the full data cube at a time. Theseportions of the full data cube are stored and then later processed togenerate a full data cube.

Various embodiments disclosed herein describe a divided-apertureinfrared spectral imaging (DAISI) system that is structured and adaptedto provide identification of target chemical contents of the imagedscene. The system is based on spectrally-resolved imaging and canprovide such identification with a single-shot (also referred to as asnapshot) comprising a plurality of images having different wavelengthcompositions that are obtained generally simultaneously. Without anyloss of generality, snapshot refers to a system in which most of thedata elements that are collected are continuously viewing the lightemitted from the scene. In contrast in scanning systems, at any giventime only a minority of data elements are continuously viewing a scene,followed by a different set of data elements, and so on, until the fulldataset is collected. Relatively fast operation can be achieved in asnapshot system because it does not need to use spectral or spatialscanning for the acquisition of infrared (IR) spectral signatures of thetarget chemical contents. Instead, IR detectors (such as, for example,infrared focal plane arrays or FPAs) associated with a plurality ofdifferent optical channels having different wavelength profiles can beused to form a spectral cube of imaging data. Although spectral data canbe obtained from a single snapshot comprising multiple simultaneouslyacquired images corresponding to different wavelength ranges, in variousembodiments, multiple snap shots may be obtained. In variousembodiments, these multiple snapshots can be averaged. Similarly, incertain embodiments multiple snap shots may be obtained and a portion ofthese can be selected and possibly averaged. Also, in contrast tocommonly used IR spectral imaging systems, the DAISI system does notrequire cooling. Accordingly, it can advantageously use uncooledinfrared detectors. For example, in various implementations, the imagingsystems disclosed herein do not include detectors configured to becooled to a temperature below 300 Kelvin. As another example, in variousimplementations, the imaging systems disclosed herein do not includedetectors configured to be cooled to a temperature below 273 Kelvin. Asyet another example, in various implementations, the imaging systemsdisclosed herein do not include detectors configured to be cooled to atemperature below 250 Kelvin. As another example, in variousimplementations, the imaging systems disclosed herein do not includedetectors configured to be cooled to a temperature below 200 Kelvin.

Implementations disclosed herein provide several advantages overexisting IR spectral imaging systems, most if not all of which mayrequire FPAs that are highly sensitive and cooled in order tocompensate, during the optical detection, for the reduction of thephoton flux caused by spectrum-scanning operation. The highly sensitiveand cooled FPA systems are expensive and require a great deal ofmaintenance. Since various embodiments disclosed herein are configuredto operate in single-shot acquisition mode without spatial and/orspectral scanning, the instrument can receive photons from a pluralityof points (e.g., every point) of the object substantiallysimultaneously, during the single reading. Accordingly, the embodimentsof imaging system described herein can collect a substantially greateramount of optical power from the imaged scene (for example, an order ofmagnitude more photons) at any given moment in time especially incomparison with spatial and/or spectral scanning systems. Consequently,various embodiments of the imaging systems disclosed herein can beoperated using uncooled detectors (for example, FPA unit including anarray of microbolometers) that are less sensitive to photons in the IRbut are well fit for continuous monitoring applications. For example, invarious implementations, the imaging systems disclosed herein do notinclude detectors configured to be cooled to a temperature below 300Kelvin. As another example, in various implementations, the imagingsystems disclosed herein do not include detectors configured to becooled to a temperature below 273 Kelvin. As yet another example, invarious implementations, the imaging systems disclosed herein do notinclude detectors configured to be cooled to a temperature below 250Kelvin. As another example, in various implementations, the imagingsystems disclosed herein do not include detectors configured to becooled to a temperature below 200 Kelvin. Imaging systems includinguncooled detectors can be capable of operating in extreme weatherconditions, require less power, are capable of operation during day andnight, and are less expensive. Some embodiments described herein canalso be less susceptible to motion artifacts in comparison withspatially and/or spectrally scanning systems which can cause errors ineither the spectral data, spatial data, or both.

In various embodiments disclosed herein, the DAISI system can be mobile.For example, the DAISI system can be configured to be worn or carried bya person, e.g., the DAISI system can be miniaturized to fit in arelatively small housing or compartment. For example, the components ofthe DAISI system can be sized and shaped to fit within small dimensionsand can have a mass sufficiently small to enable the human user to carryor wear the system without undue exertion. As explained herein, in someembodiments, the DAISI system can be sized and shaped to fit within avolume of less than about 300 cubic inches, or in some embodiments, lessthan about 200 cubic inches. In still other embodiments, the DAISIsystem can be sized and shaped to fit within a volume less than about100 cubic inches. For example, in some arrangements, the DAISI systemcan be sized and shaped to fit within a volume in a range of about 50cubic inches to about 300 cubic inches. In other arrangements, the DAISIsystem can be sized and shaped to fit within a volume in a range ofabout 80 cubic inches to about 200 cubic inches.

Advantageously, such a portable and/or wearable DAISI system can enablethe user to monitor installations in remote locations and to detect thepresence of various gases (e.g., poisonous gases) in real-time. Further,the portable DAISI system can enable the user to travel to differentinstallations to monitor the presence of gases or chemicals in multiplelocations. For example, the user may travel to an oil drillinginstallation in which oil is pumped from the ground. The user can carryor attach the portable DAISI system to his or her clothing or body(e.g., by way of a clip, hat, etc.) and can activate the system while heor she is on-site. Optical components on board the portable DAISI systemcan capture one or more snapshot multispectral images of portions of theinstallation susceptible to gas or chemical leaks. Computing units onboard the portable DAISI system can process the captured multispectralimage data to detect and/or classify gases or chemicals present at thesite. A communications module can notify the user of the detected gases.For example, in various embodiments, the communications module can senda notification to a user interface (such as a set of computingeyeglasses, a mobile computing device such as a mobile smartphone, atablet computing device, a laptop computing device, or any othersuitable interface), and the user interface can display informationabout the detected gases to the user in real-time, e.g., at the oildrilling installation.

II. Examples of Divided Aperture Infrared Spectral Imager Systems

FIG. 1 provides a diagram schematically illustrating spatial andspectral division of incoming light by an embodiment 100 of a dividedaperture infrared spectral imager (DAISI) system that can image anobject 110 possessing IR spectral signature(s). The system 100 includesa front objective lens 124, an array of optical filters 130, an array ofreimaging lenses 128 and a detector array 136. In various embodiments,the detector array 136 can include a single FPA or an array of FPAs.Each detector in the detector array 136 can be disposed at the focus ofeach of the lenses in the array of reimaging lenses 128. In variousembodiments, the detector array 136 can include a plurality ofphoto-sensitive devices. In some embodiments, the plurality ofphoto-sensitive devices may comprise a two-dimensional imaging sensorarray that is sensitive to radiation having wavelengths between 1 μm and20 μm (for example, in near infra-red wavelength range, mid infra-redwavelength range, or long infra-red wavelength range,). In variousembodiments, the plurality of photo-sensitive devices can include CCD orCMOS sensors, bolometers, microbolometers or other detectors that aresensitive to infra-red radiation.

An aperture of the system 100 associated with the front objective lenssystem 124 is spatially and spectrally divided by the combination of thearray of optical filters 130 and the array of reimaging lenses 128. Invarious embodiments, the combination of the array of optical filters 130and the array of reimaging lenses 128 can be considered to form aspectrally divided pupil that is disposed forward of the opticaldetector array 136. The spatial and spectral division of the apertureinto distinct aperture portions forms a plurality of optical channels120 along which light propagates. In various embodiments, the array 128of re-imaging lenses 128 a and the array of spectral filters 130 whichrespectively correspond to the distinct optical channels 120. Theplurality of optical channels 120 can be spatially and/or spectrallydistinct. The plurality of optical channels 120 can be formed in theobject space and/or image space. In one implementation, the distinctchannels 120 may include optical channels that are separated angularlyin space. The array of spectral filters 130 may additionally include afilter-holding aperture mask (comprising, for example, IR light-blockingmaterials such as ceramic, metal, or plastic). Light from the object 110(for example a cloud of gas), the optical properties of which in the IRare described by a unique absorption, reflection and/or emissionspectrum, is received by the aperture of the system 100. This lightpropagates through each of the plurality of optical channels 120 and isfurther imaged onto the optical detector array 136. In variousimplementations, the detector array 136 can include at least one FPA. Invarious embodiments, each of the re-imaging lenses 128 a can bespatially aligned with a respectively-corresponding spectral region. Inthe illustrated implementation, each filter element from the array ofspectral filters 130 corresponds to a different spectral region. Eachre-imaging lens 128 a and the corresponding filter element of the arrayof spectral filter 130 can coincide with (or form) a portion of thedivided aperture and therefore with respectively-corresponding spatialchannel 120. Accordingly, in various embodiment an imaging lens 128 aand a corresponding spectral filter can be disposed in the optical pathof one of the plurality of optical channels 120. Radiation from theobject 110 propagating through each of the plurality of optical channels120 travels along the optical path of each re-imaging lens 128 a and thecorresponding filter element of the array of spectral filter 130 and isincident on the detector array (e.g., FPA component) 136 to form asingle image (e.g., sub-image) of the object 110. The image formed bythe detector array 136 generally includes a plurality of sub-imagesformed by each of the optical channels 120. Each of the plurality ofsub-images can provide different spatial and spectral information of theobject 110. The different spatial information results from some parallaxbecause of the different spatial locations of the smaller apertures ofthe divided aperture. In various embodiments, adjacent sub-images can becharacterized by close or substantially equal spectral signatures. Thedetector array (e.g., FPA component) 136 is further operably connectedwith a processor 150 (not shown). The processor 150 can be programmed toaggregate the data acquired with the system 100 into a spectral datacube. The data cube represents, in spatial (x, y) and spectral (λ)coordinates, an overall spectral image of the object 110 within thespectral region defined by the combination of the filter elements in thearray of spectral filters 130. Additionally, in various embodiments, theprocessor or processing electronics 150 may be programmed to determinethe unique absorption characteristic of the object 110. Also, theprocessor/processing electronics 150 can, alternatively or in addition,map the overall image data cube into a cube of data representing, forexample, spatial distribution of concentrations, c, of targeted chemicalcomponents within the field of view associated with the object 110.

Various implementations of the embodiment 100 can include an optionalmoveable temperature-controlled reference source 160 including, forexample, a shutter system comprising one or more reference shuttersmaintained at different temperatures. The reference source 160 caninclude a heater, a cooler or a temperature-controlled elementconfigured to maintain the reference source 160 at a desiredtemperature. For example, in various implementations, the embodiment 100can include two reference shutters maintained at different temperatures.The reference source 160 is removably and, in one implementation,periodically inserted into an optical path of light traversing thesystem 100 from the object 110 to the detector array (e.g., FPAcomponent) 136 along at least one of the channels 120. The removablereference source 160 thus can block such optical path. Moreover, thisreference source 160 can provide a reference IR spectrum to recalibratevarious components including the detector array 136 of the system 100 inreal time. The configuration of the moveable reference source 160 isfurther discussed below.

In the embodiment 100, the front objective lens system 124 is shown toinclude a single front objective lens positioned to establish a commonfield-of-view (FOV) for the reimaging lenses 128 a and to define anaperture stop for the whole system. In this specific case, the aperturestop substantially spatially coincides with and/or is about the samesize as or slightly larger than the plurality of smaller limitingapertures corresponding to different optical channels 120. As a result,the positions for spectral filters of the different optical channels 120coincide with the position of the aperture stop of the whole system,which in this example is shown as a surface between the lens system 124and the array 128 of the reimaging lenses 128 a. In variousimplementations, the lens system 124 can be an objective lens 124.However, the objective lens 124 is optional and various embodiments ofthe system 100 need not include the objective lens 124. In variousembodiments, the objective lens 124 can slightly shift the imagesobtained by the different detectors in the array 136 spatially along adirection perpendicular to optical axis of the lens 124, thus thefunctionality of the system 100 is not necessarily compromised when theobjective lens 124 is not included. Generally, however, the fieldapertures corresponding to different optical channels may be located inthe same or different planes. These field apertures may be defined bythe aperture of the reimaging lens 128 a and/or filters in the dividedaperture 130 in certain implementations. In one implementation, thefield apertures corresponding to different optical channels can belocated in different planes and the different planes can be opticalconjugates of one another. Similarly, while all of the filter elementsin the array of spectral filters 130 of the embodiment 100 are shown tolie in one plane, generally different filter elements of the array ofspectral filter 130 can be disposed in different planes. For example,different filter elements of the array of spectral filters 130 can bedisposed in different planes that are optically conjugate to oneanother. However, in other embodiments, the different filter elementscan be disposed in non-conjugate planes.

In contrast to the embodiment 100, the front objective lens 124 need notbe a single optical element, but instead can include a plurality oflenses 224 as shown in an embodiment 200 of the DAISI imaging system inFIG. 2. These lenses 224 are configured to divide an incoming opticalwavefront from the object 110. For example, the array of front objectivelenses 224 can be disposed so as to receive an IR wavefront emitted bythe object that is directed toward the DAISI system. The plurality offront objective lenses 224 divide the wavefront spatially intonon-overlapping sections. FIG. 2 shows three objective lenses 224 in afront optical portion of the optical system contributing to the spatialdivision of the aperture of the system in this example. The plurality ofobjective lenses 224, however, can be configured as a two-dimensional(2D) array of lenses. FIG. 2 presents a general view of the imagingsystem 200 and the resultant field of view of the imaging system 200. Anexploded view 202 of the imaging system 200 is also depicted in greaterdetail in a figure inset of FIG. 2. As illustrated in the detailed view202, the embodiment of the imaging system 200 includes a field reference204 at the front end of the system. The field reference 204 can be usedto truncate the field of view. The configuration illustrated in FIG. 2has an operational advantage over embodiment 100 of FIG. 1 in that theoverall size and/or weight and/or cost of manufacture of the embodiment200 can be greatly reduced because the objective lens is smaller. Eachpair of the lenses in the array 224 and the array 128 is associated witha field of view (FOV). Each pair of lenses in the array 224 and thearray 128 receives light from the object from a different angle.Accordingly, the FOV of the different pairs of lenses in the array 224and the array 128 do not completely overlap as a result of parallax. Asthe distance between the imaging system 200 (portion 202) and the object110 increases, the overlapping region 230 between the FOVs of theindividual lenses 224 increases while the amount of parallax 228 remainsapproximately the same, thereby reducing its effect on the system 200.When the ratio of the parallax-to-object-distance is substantially equalto the pixel-size-to-system-focal-length ratio then the parallax effectmay be considered to be negligible and, for practical purposes, nolonger distinguishable. While the lenses 224 are shown to be disposedsubstantially in the same plane, optionally different objective lensesin the array of front objective lenses 224 can be disposed in more thanone plane. For example, some of the individual lenses 224 can bedisplaced with respect to some other individual lenses 224 along theaxis 226 (not shown) and/or have different focal lengths as compared tosome other lenses 224. As discussed below, the field reference 204 canbe useful in calibrating the multiple detectors 236.

In one implementation, the front objective lens system such as the arrayof lenses 224 is configured as an array of lenses integrated or moldedin association with a monolithic substrate. Such an arrangement canreduce the costs and complexity otherwise accompanying the opticaladjustment of individual lenses within the system. An individual lens224 can optionally include a lens with varying magnification. As oneexample, a pair of thin and large diameter Alvarez plates can be used inat least a portion of the front objective lens system. Without any lossof generality, the Alvarez plates can produce a change in focal lengthwhen translated orthogonally with respect to the optical beam.

In further reference to FIG. 1, the detector array 136 (e.g., FPAcomponent) configured to receive the optical data representing spectralsignature(s) of the imaged object 110 can be configured as a singleimaging array (e.g., FPA) 136. This single array may be adapted toacquire more than one image (formed by more than one optical channel120) simultaneously. Alternatively, the detector array 136 may include aFPA unit. In various implementations, the FPA unit can include aplurality of optical FPAs. At least one of these plurality of FPAs canbe configured to acquire more than one spectrally distinct image of theimaged object. For example, as shown in the embodiment 200 of FIG. 2, invarious embodiments, the number of FPAs included in the FPA unit maycorrespond to the number of the front objective lenses 224. In theembodiment 200 of FIG. 2, for example, three FPAs 236 are providedcorresponding to the three objective lenses 224. In one implementationof the system, the FPA unit can include an array of microbolometers. Theuse of multiple microbolometers advantageously allows for an inexpensiveway to increase the total number of detection elements (i.e. pixels) forrecording of the three-dimensional data cube in a single acquisitionevent (i.e. one snapshot). In various embodiments, an array ofmicrobolometers more efficiently utilizes the detector pixels of thearray of FPAs (e.g., each FPA) as the number of unused pixels isreduced, minimized and/or eliminated between the images that may existwhen using a single microbolometer.

FIG. 3A illustrates schematically an embodiment 300 of the imagingsystem in which the number of the front objective lenses 324 a in thelens array 324, the number of re-imaging lenses 128 a in the lens array128, and the number of FPAs 336 are the same. So configured, eachcombination of respectively corresponding front objective lens 324,re-imaging lens 128 a, and FPAs 336 constitutes an individual imagingchannel. Such a channel is associated with acquisition of the IR lighttransmitted from the object 110 through an individual filter element ofthe array of optical filters 130. A field reference 338 of the system300 is configured to have a uniform temperature across its surface andbe characterized by a predetermined spectral curve of radiationemanating therefrom. In various implementations, the field reference 338can be used as a calibration target to assist in calibrating ormaintaining calibration of the FPA. Accordingly, in variousimplementations, the field reference 338 is used for dynamicallyadjusting the data output from each FPA 336 after acquisition of lightfrom the object 110. This dynamic calibration process helps provide thatoutput of the different (e.g., most, or each of the) FPA 336 representscorrect acquired data, with respect to the other FPAs 336 for analysis,as discussed below in more detail.

FIG. 3B illustrates the plan view perpendicular to the axis 226 of anembodiment 300 of the imaging system illustrated in FIG. 3A. For theembodiment shown in FIG. 3B, the optical components (e.g., objectivelenses 324 a, filter elements of the array of spectral filters 130,re-imaging lenses 128 a and FPA units 336) are arranged as a 4×3 array.In one implementation, the 4×3 array 340 of optical components (lenses324 a, 128 a; detector elements 336) is used behind the temperaturecontrolled reference target 160. The field reference aperture 338 can beadapted to obscure and/or block a peripheral portion of the bundle oflight propagating from the object 110 towards the FPA units 336. As aresult, the field reference 338 obscures and/or blocks the border orperipheral portion(s) of the images of the object 110 formed on the FPAelements located along the perimeter 346 of the detector system.Generally, two elements of the FPA unit will produce substantially equalvalues of digital counts when they are used to observe the same portionof the scene in the same spectral region using the same optical train.If any of these input parameters (for example, scene to be observed,spectral content of light from the scene, or optical elements deliveringlight from the scene to the two detector elements) differ, the countsassociated with the elements of the FPA unit will differ as well.Accordingly, and as an example, in a case when the two FPAs of the FPAunit 336 (such as those denoted as #6 and #7 in FIG. 3B) remainsubstantially un-obscured by the field reference 338, the outputs fromthese FPAs can be dynamically adjusted to the output from one of theFPAs located along perimeter 346 (such as, for example, the FPA element#2 or FPA element #11) that processes light having similar spectralcharacteristics.

FIG. 4 illustrates schematically a portion of another embodiment of animaging system 400 that contains an array 424 of front objective lenses424 a. The array 424 of lenses 424 a adapted to receive light from theobject 110 and relay the received light to the array 128 of re-imaginglenses 128 a through an array 438 of field references (or field stops)438 a, and through an array 440 of the relay lenses. The spectralcharacteristics of the field references/field stops 438 a can be known.The field references 438 a are disposed at corresponding intermediateimage planes defined, with respect to the object 110, by respectivelycorresponding front objective lenses 424 a. When refractivecharacteristics of all of the front objective lenses 424 a aresubstantially the same, all of the field references 438 a are disposedin the same plane. A field reference 438 a of the array 438 obscures (orcasts a shadow on) a peripheral region of a corresponding image (e.g.,sub-image) formed at the detector plane 444 through a respectivelycorresponding spatial imaging channel 450 of the system 400 prior tosuch image being spectrally processed by the processor 150. The array440 of relay lenses then transmits light along each of the imagingchannels 450 through different spectral filters 454 a of the filterarray 454, past the calibration apparatus that includes two temperaturecontrolled shutters 460 a, 460 b, and then onto the detector module 456.In various embodiments, the detector module 456 can include amicrobolometer array or some other IR FPA.

The embodiment 400 has several operational advantages. It is configuredto provide a spectrally known object within every image (e.g.,sub-image) and for every snapshot acquisition which can be calibratedagainst. Such spectral certainty can be advantageous when using an arrayof IR FPAs like microbolometers, the detection characteristics of whichcan change from one imaging frame to the next due to, in part, changesin the scene being imaged as well as the thermal effects caused byneighboring FPAs. In various embodiments, the field reference array 438of the embodiment 400—can be disposed within the Rayleigh range(approximately corresponding to the depth of focus) associated with thefront objective lenses 424, thereby removing unusable blurred pixels dueto having the field reference outside of this range. Additionally, theembodiment 400 of FIG. 4 can be more compact than, for example, theconfiguration 300 of FIG. 3A. In the system shown in FIG. 3A, forexample, the field reference 338 may be separated from the lens array324 by a distance greater than several (for example, five) focal lengthsto minimize/reduce blur contributed by the field reference to an imageformed at a detector plane.

In various embodiments, the multi-optical FPA unit of the IR imagingsystem can additionally include an FPA configured to operate in avisible portion of the spectrum. In reference to FIG. 1, for example, animage of the scene of interest formed by such visible-light FPA may beused as a background to form a composite image by overlapping an IRimage with the visible-light image. The IR image may be overlappedvirtually, with the use of a processor and specifically-designedcomputer program product enabling such data processing, or actually, bya viewer. The IR image may be created based on the image data acquiredby the individual FPAs 136. The so-formed composite image facilitatesthe identification of the precise spatial location of the targetspecies, the spectral signatures of which the system is able todetect/recognize.

Optical Filters.

The optical filters, used with an embodiment of the system, that definespectrally-distinct IR image (e.g., sub-image) of the object can employabsorption filters, interference filters, and Fabry-Perot etalon basedfilters, to name just a few. When interference filters are used, theimage acquisition through an individual imaging channel defined by anindividual re-imaging lens (such as a lens 128 a of FIGS. 1, 2, 3, and4) may be carried out in a single spectral bandwidth or multiplespectral bandwidths. Referring again to the embodiments 100, 200, 300,400 of FIGS. 1 through 4, and in further reference to FIG. 3B, examplesof a 4-by-3 array of spectral filters 130 is shown in FIGS. 5A and 5B.Individual filters 1 through 12 are juxtaposed with a supportingopto-mechanical element (not shown) to define a filter-array plane thatis oriented, in operation, substantially perpendicularly to the generaloptical axis 226 of the imaging system. In various implementations, theindividual filters 1 through 12 need not be discrete optical components.Instead, the individual filters 1 through 12 can comprise one or morecoatings that are applied to one or more surfaces of the reimaginglenses (such as a lens 128 a of FIGS. 1, 2, 3, and 4) or the surfaces ofone or more detectors.

The optical filtering configuration of various embodiments disclosedherein may advantageously use a bandpass filter defining a specifiedspectral band. Any of the filters 0 a through 3 a, the transmissioncurves of which are shown in FIG. 6A may, for example, be used. Thefilters may be placed in front of the optical FPA (or generally, betweenthe optical FPA and the object). In particular, and in further referenceto FIGS. 1, 2 3, and 4, when optical detector arrays 136, 236, 336, 456include microbolometers, the predominant contribution to noiseassociated with image acquisition is due to detector noise. Tocompensate and/or reduce the noise, various embodiments disclosed hereinutilize spectrally-multiplexed filters. In various implementations, thespectrally-multiplexed filters can comprise a plurality of long passfilters, a plurality long pass filters, a plurality of band pass filtersand any combinations thereof. An example of the spectral transmissioncharacteristics of spectrally-multiplexed filters 0 b through 3 d foruse with various embodiments of imaging systems disclosed herein isdepicted in FIG. 6B. Filters of FIG. 6C can be referred to aslong-wavelength pass, LP filters. An LP filter generally attenuatesshorter wavelengths and transmits (passes) longer wavelengths (e.g.,over the active range of the target IR portion of the spectrum). Invarious embodiments, short-wavelength-pass filters, SP, may also beused. An SP filter generally attenuates longer wavelengths and transmits(passes) shorter wavelengths (e.g., over the active range of the targetIR portion of the spectrum). At least in part due to thesnap-shot/non-scanning mode of operation, embodiments of the imagingsystem described herein can use less sensitive microbolometers withoutcompromising the SNR. The use of microbolometers, asdetector-noise-limited devices, in turn not only benefits from the useof spectrally multiplexed filters, but also does not require cooling ofthe imaging system during normal operation.

Referring again to FIGS. 6A, 6B, 6C, and 6D, each of the filters (0 b .. . 3 d) transmits light in a substantially wider region of theelectromagnetic spectrum as compared to those of the filters (0 a . . .3 a). Accordingly, when the spectrally-multiplexed set of filters (0 b .. . 0 d) is used with an embodiment of the imaging system, the overallamount of light received by the FPAs (for example, 236, 336) is largerthan would be received when using the bandpass filters (0 a . . . 4 a).This “added” transmission of light defined by the use of thespectrally-multiplexed LP (or SP) filters facilitates an increase of thesignal on the FPAs above the level of the detector noise. Additionally,by using, in an embodiment of the imaging system, filters havingspectral bandwidths greater than those of band-pass filters, theuncooled FPAs of the embodiment of the imaging system experience lessheating from radiation incident thereon from the imaged scene and fromradiation emanating from the FPA in question itself. This reducedheating is due to a reduction in the back-reflected thermal emission(s)coming from the FPA and reflecting off of the filter from thenon-band-pass regions. As the transmission region of the multiplexed LP(or SP) filters is wider, such parasitic effects are reduced therebyimproving the overall performance of the FPA unit.

In one implementation, the LP and SP filters can be combined, in aspectrally-multiplexed fashion, in order to increase or maximize thespectral extent of the transmission region of the filter system of theembodiment.

The advantage of using spectrally multiplexed filters is appreciatedbased on the following derivation, in which a system of M filters isexamined (although it is understood that in practice an embodiment ofthe invention can employ any number of filters). As an illustrativeexample, the case of M=7 is considered. Analysis presented below relatesto one spatial location in each of the images (e.g., sub-images) formedby the differing imaging channels (e.g., different optical channels 120)in the system. A similar analysis can be performed for each point at animage (e.g., sub-image), and thus the analysis can be appropriatelyextended as required.

The unknown amount of light within each of the M spectral channels(corresponding to these M filters) is denoted with f₁, f₂, f₃, . . .f_(M), and readings from corresponding detector elements receiving lighttransmitted by each filter is denoted as g₁, g₂, g₃ . . . g_(M), whilemeasurement errors are represented by n₁, n₂, n₃, . . . n_(M). Then, thereadings at the seven FPA pixels each of which is optically filtered bya corresponding band-pass filter of FIG. 6A can be represented by:

g ₁ =f ₁ +n ₁,

g ₂ =f ₂ +n ₂,

g ₃ =f ₃ +n ₃,

g ₄ =f ₄ +n ₄,

g ₅ =f ₅ +n ₅,

g ₆ =f ₆ +n ₆,

g ₇ =f ₇ +n ₇,

These readings (pixel measurements) g_(i) are estimates of the spectralintensities f_(i). The estimates g_(i) are not equal to thecorresponding f_(i) values because of the measurement errors n_(i).However, if the measurement noise distribution has zero mean, then theensemble mean of each individual measurement can be considered to beequal to the true value, i.e. <g_(i)>=f_(i). Here, the angle bracketsindicate the operation of calculating the ensemble mean of a stochasticvariable. The variance of the measurement can, therefore, be representedas:

((g _(i) −f _(i))²)=(n _(i) ²)=σ²

In embodiments utilizing spectrally-multiplexed filters, in comparisonwith the embodiments utilizing band-pass filters, the amount of radiantenergy transmitted by each of the spectrally-multiplexed LP or SPfilters towards a given detector element can exceed that transmittedthrough a spectral band of a band-pass filter. In this case, theintensities of light corresponding to the independent spectral bands canbe reconstructed by computational means. Such embodiments can bereferred to as a “multiplex design”.

One matrix of such “multiplexed filter” measurements includes a Hadamardmatrix requiring “negative” filters that may not be necessarilyappropriate for the optical embodiments disclosed herein. An S-matrixapproach (which is restricted to having a number of filters equal to aninteger that is multiple of four minus one) or a row-doubled Hadamardmatrix (requiring a number of filters to be equal to an integer multipleof eight) can be used in various embodiments. Here, possible numbers offilters using an S-matrix setup are 3, 7, 11, etc and, if a row-doubledHadamard matrix setup is used, then the possible number of filters is 8,16, 24, etc. For example, the goal of the measurement may be to measureseven spectral band f_(i) intensities using seven measurements g_(i) asfollows:

g ₁ =f ₁+0+f ₃+0+f ₅+0+f ₇ +n ₁,

g ₂=+0+f ₂ +f ₃+0+0+f ₆ +f ₇ +n ₂,

g ₃ =f ₁ +f ₂+0+0+f ₅+0+f ₇ +n ₃,

g ₄=0+0+0+=f ₄ +f ₅ +f ₆ +f ₇ +n ₄,

g ₅ =f ₁+0+f ₃ +f ₄+0+f ₆+0+n ₅,

g ₆=0+f ₂ +f ₃ +f ₄ +f ₅+0+0+n ₆,

g ₇ =f ₁ +f ₂++0+f ₄+0+0+f ₇ +n ₇

Optical transmission characteristics of the filters described above aredepicted in FIG. 6B. Here, a direct estimate of the f_(i) is no longerprovided through a relationship similar to <g_(i)>=f_(i). Instead, if a“hat” notation is used to denote an estimate of a given value, then alinear combination of the measurements can be used such as, for example,

{circumflex over (f)} ₁=¼(+g ₁ −g ₂ +g ₃ −g ₄ +g ₅ −g ₆ +g ₇),

{circumflex over (f)} ₂=¼(−g ₁ +g ₂ +g ₃ −g ₄ −g ₅ +g ₆ +g ₇),

{circumflex over (f)} ₃=¼(+g ₁ +g ₂ −g ₃ −g ₄ +g ₅ −g ₆ −g ₇),

{circumflex over (f)} ₄=¼(g ₁ g ₂ g ₃ |g ₄ |g ₅ |g ₆ |g ₇),

{circumflex over (f)} ₅=¼(+g ₁ −g ₂ +g ₃ +g ₄ −g ₅ +g ₆ −g ₇),

{circumflex over (f)} ₆=¼(−g ₁ +g ₂ +g ₃ −g ₄ +g ₅ −g ₆ −g ₇),

{circumflex over (f)} ₇=¼(+g ₁ +g ₂ −g ₃ +g ₄ −g ₅ −g ₆ +g ₇),

These {circumflex over (f)}_(i) are unbiased estimates when the n_(i)are zero mean stochastic variables, so that <{circumflex over(f)}_(i)−f_(i)>=0. The measurement variance corresponding to i^(th)measurement is given by the equation below:

(({circumflex over (f)} _(i) −f _(i))²)= 7/16σ²

From the above equation, it is observed that by employingspectrally-multiplexed system the signal-to-noise ratio (SNR) of ameasurement is improved by a factor of √{square root over (16/7)}=1.51.

For N channels, the SNR improvement achieved with aspectrally-multiplexed system can be expressed as (N+1)/(2√{square rootover (N)}). For example, an embodiment employing 12 spectral channels(N=12) is characterized by a SNR improvement, over anon-spectrally-multiplexed system, comprising a factor of up to 1.88.

Two additional examples of related spectrally-multiplexed filterarrangements 0 c through 3 c and 0 d through 3 d that can be used invarious embodiments of the imaging systems described herein are shown inFIGS. 6C and 6D, respectively. The spectrally-multiplexed filters shownin FIGS. 6C and 6D can be used in embodiments of imaging systemsemploying uncooled FPAs (such as microbolometers). FIG. 6C illustrates aset of spectrally-multiplexed long-wavelength pass (LP) filters used inthe system. An LP filter generally attenuates shorter wavelengths andtransmits (passes) longer wavelengths (e.g., over the active range ofthe target IR portion of the spectrum). A single spectral channel havinga transmission characteristic corresponding to the difference betweenthe spectral transmission curves of at least two of these LP filters canbe used to procure imaging data for the data cube using an embodiment ofthe system described herein. In various implementations, the spectralfilters disposed with respect to the different FPAs can have differentspectral characteristics. In various implementations, the spectralfilters may be disposed in front of only some of the FPAs while theremaining FPAs may be configured to receive unfiltered light. Forexample, in some implementations, only 9 of the 12 detectors in the 4×3array of detectors described above may be associated with a spectralfilter while the other 3 detectors may be configured to receivedunfiltered light. Such a system may be configured to acquire spectraldata in 10 different spectral channels in a single data acquisitionevent.

The use of microbolometers, as detector-noise-limited devices, in turnnot only can benefit from the use of spectrally multiplexed filters, butalso does not require cooling of the imaging system during normaloperation. In contrast to imaging systems that include highly sensitiveFPA units with reduced noise characteristics, the embodiments of imagingsystems described herein can employ less sensitive microbolometerswithout compromising the SNR. This result is at least in part due to thesnap-shot/non-scanning mode of operation.

As discussed above, an embodiment may optionally, and in addition to atemperature-controlled reference unit (for example temperaturecontrolled shutters such as shutters 160, 460 a, 460 b), employ a fieldreference component (e.g., field reference aperture 338 in FIG. 3A), oran array of field reference components (e.g., filed reference apertures438 in FIG. 4), to enable dynamic calibration. Such dynamic calibrationcan be used for spectral acquisition of one or more or every data cube.Such dynamic calibration can also be used for a spectrally-neutralcamera-to-camera combination to enable dynamic compensation of parallaxartifacts. The use of the temperature-controlled reference unit (forexample, temperature-controlled shutter system 160) and field-referencecomponent(s) facilitates maintenance of proper calibration of each ofthe FPAs individually and the entire FPA unit as a whole.

In particular, and in further reference to FIGS. 1, 2, 3, and 4, thetemperature-controlled unit generally employs a system having first andsecond temperature zones maintained at first and second differenttemperatures. For example, shutter system of each of the embodiments100, 200, 300 and 400 can employ not one but at least twotemperature-controlled shutters that are substantially parallel to oneanother and transverse to the general optical axis 226 of theembodiment(s) 100, 200, 300, 400. Two shutters at two differenttemperatures may be employed to provide more information forcalibration; for example, the absolute value of the difference betweenFPAs at one temperature as well as the change in that difference withtemperature change can be recorded. Referring, for example, to FIG. 4,in which such multi-shutter structure is shown, the use of multipleshutters enables the user to create a known reference temperaturedifference perceived by the FPAs 456. This reference temperaturedifference is provided by the IR radiation emitted by the shutter(s) 460a, 460 b when these shutters are positioned to block the radiation fromthe object 110. As a result, not only the offset values corresponding toeach of the individual FPAs pixels can be adjusted but also the gainvalues of these FPAs. In an alternative embodiment, the system havingfirst and second temperature zones may include a single or multi-portionpiece. This single or multi-portion piece may comprise for example aplate. This piece may be mechanically-movable across the optical axiswith the use of appropriate guides and having a first portion at a firsttemperature and a second portion at a second temperature.

Indeed, the process of calibration of an embodiment of the imagingsystem starts with estimating gain and offset by performing measurementsof radiation emanating, independently, from at least twotemperature-controlled shutters of known and different radiances. Thegain and offset can vary from detector pixel to detector pixel.Specifically, first the response of the detector unit 456 to radiationemanating from one shutter is carried out. For example, the firstshutter 460 a blocks the FOV of the detectors 456 and the temperature T₁is measured directly and independently with thermistors. Following suchinitial measurement, the first shutter 460 a is removed from the opticalpath of light traversing the embodiment and another second shutter (forexample, 460 b) is inserted in its place across the optical axis 226 toprevent the propagation of light through the system. The temperature ofthe second shutter 460 b can be different than the first shutter(T₂≠T₁). The temperature of the second shutter 460 b is alsoindependently measured with thermistors placed in contact with thisshutter, and the detector response to radiation emanating from theshutter 460 b is also recorded. Denoting operational response of FPApixels (expressed in digital numbers, or “counts”) as g_(i) to a sourceof radiance L_(i), the readings corresponding to the measurements of thetwo shutters can be expressed as:

g ₁ =γL ₁(T ₁)+g _(offset)

g ₂ =γL ₂(T ₂)+g _(offset)

Here, g_(offset) is the pixel offset value (in units of counts), and γis the pixel gain value (in units of counts per radiance unit). Thesolutions of these two equations with respect to the two unknownsg_(offset) and γ can be obtained if the values of g₁ and g₂ and theradiance values L₁ and L₂ are available. These values can, for example,be either measured by a reference instrument or calculated from theknown temperatures T₁ and T₂ together with the known spectral responseof the optical system and FPA. For any subsequent measurement, one canthen invert the equation(s) above in order to estimate the radiancevalue of the object from the detector measurement, and this can be donefor each pixel in each FPA within the system.

As already discussed, and in reference to FIGS. 1 through 4, thefield-reference apertures may be disposed in an object space or imagespace of the optical system, and dimensioned to block a particularportion of the IR radiation received from the object. In variousimplementations, the field-reference aperture, the opening of which canbe substantially similar in shape to the boundary of the filter array(for example, and in reference to a filter array of FIGS. 3B, 5B—e.g.,rectangular). The field-reference aperture can be placed in front of theobjective lens (124, 224, 324, 424) at a distance that is at leastseveral times (in one implementation—at least five times) larger thanthe focal length of the lens such that the field-reference aperture isplaced closer to the object. Placing the field-reference aperture closerto the object can reduce the blurriness of the image. In the embodiment400 of FIG. 4, the field-reference aperture can be placed within thedepth of focus of an image conjugate plane formed by the front objectivelens 424. The field reference, generally, can facilitate, effectuatesand/or enable dynamic compensation in the system by providing aspectrally known and temporally-stable object within every scene toreference and stabilize the output from the different FPAs in the array.

Because each FPA's offset value is generally adjusted from each frame tothe next frame by the hardware, comparing the outputs of one FPA withanother can have an error that is not compensated for by the staticcalibration parameters g_(offset) and γ established, for example, by themovable shutters 160. In order to ensure that FPAs operate inradiometric agreement over time, it is advantageous for a portion ofeach detector array to view a reference source (such as the fieldreference 338 in FIG. 3A, for example) over a plurality of framesobtained over time. If the reference source spectrum is known a priori(such as a blackbody source at a known temperature), one can measure theresponse of each FPA to the reference source in order to estimatechanges to the pixel offset value. However, the temperature of thereference source need not be known. In such implementations, dynamiccalibration of the different detectors can be performed by monitoringthe change in the gain and the offset for the various detectors from thetime the movable shutters used for static calibration are removed. Anexample calculation of the dynamic offset proceeds as follows.

Among the FPA elements in an array of FPAs in an embodiment of theimaging system, one FPA can be selected to be the “reference FPA”. Thefield reference temperature measured by all the other FPAs can beadjusted to agree with the field reference temperature measured by thereference as discussed below. The image obtained by each FPA includes aset of pixels obscured by the field reference 338. Using the previouslyobtained calibration parameters g_(offset) and γ (the pixel offset andgain), the effective blackbody temperature T_(i) of the field referenceas measured by each FPA is estimated using the equation below:

T _(i)=mean{(g+Δg _(i) +g _(offset)/γ}=mean{(g−g _(offset))/γ}+ΔT _(i)

Using the equation above, the mean value over all pixels that areobscured by the field reference is obtained. In the above equationΔg_(i) is the difference in offset value of the current frame fromΔf_(offset) obtained during the calibration step. For the reference FPA,Δg_(i) can be simply set to zero. Then, using the temperaturedifferences measured by each FPA, one obtains

T _(i) −T _(ref)=mean{(g+Δg _(i) +g _(offset) /γ}+ΔT _(i)−mean{(g−g_(offset))/γ}=ΔT _(i)

Once ΔT_(i) for each FPA is measured, its value can be subtracted fromeach image in order to force operational agreement between such FPA andthe reference FPA. While the calibration procedure has been discussedabove in reference to calibration of temperature, a procedurally similarmethodology of calibration with respect to radiance value can also beimplemented.

Examples of Methodology of Measurements.

Prior to optical data acquisition using an embodiment of the IR imagingsystem as described herein, one or more, most, or potentially all theFPAs of the system can be calibrated. For example, greater than 50%,60%, 70%, 80% or 90% of the FPAs 336 can be initially calibrated. Asshown in FIG. 3A, these FPAs 336 may form separate images of the objectusing light delivered in a corresponding optical channel that mayinclude the combination of the corresponding front objective andre-imaging lenses 324, 128. The calibration procedure can allowformation of individual images in equivalent units (so that, forexample, the reading from the FPA pixels can be re-calculated in unitsof temperature or radiance units, etc.). Moreover, the calibrationprocess can also allow the FPAs (e.g., each of the FPAs) to be spatiallyco-registered with one another so that a given pixel of a particular FPAcan be optically re-mapped through the optical system to the samelocation at the object as the corresponding pixel of another FPA.

To achieve at least some of these goals, a spectral differencing methodmay be employed. The method involves forming a difference image fromvarious combinations of the images from different channels. Inparticular, the images used to form difference images can be registeredby two or more different FPAs in spectrally distinct channels havingdifferent spectral filters with different spectral characteristics.Images from different channels having different spectral characteristicswill provide different spectral information. Comparing (e.g.,subtracting) these images, can therefore yield valuable spectral basedinformation. For example, if the filter element of the array of spectralfilters 130 corresponding to a particular FPA 336 transmits light fromthe object 110 including a cloud of gas, for example, with a certainspectrum that contains the gas absorption peak or a gas emission peakwhile another filter element of the array of spectral filters 130corresponding to another FPA 336 does not transmit such spectrum, thenthe difference between the images formed by the two FPAs at issue willhighlight the presence of gas in the difference image.

A shortcoming of the spectral differencing method is that contributionsof some auxiliary features associated with imaging (not just the targetspecies such as gas itself) can also be highlighted in and contribute tothe difference image. Such contributing effects include, to name just afew, parallax-induced imaging of edges of the object, influence ofmagnification differences between the two or more optical channels, anddifferences in rotational positioning and orientation between the FPAs.While magnification-related errors and FPA-rotation-caused errors can becompensated for by increasing the accuracy of the instrumentconstruction as well as by post-processing of the acquired imaging,parallax is scene-induced and is not so easily correctable. In addition,the spectral differencing method is vulnerable to radiance calibrationerrors. Specifically, if one FPA registers radiance of light from agiven feature of the object as having a temperature of 40° C., forexample, while the data from another FPA represents the temperature ofthe same object feature as being 39° C., then such feature of the objectwill be enhanced or highlighted in the difference image (formed at leastin part based on the images provided by these two FPAs) due to suchradiance-calibration error.

One solution to some of such problems is to compare (e.g., subtract)images from the same FPA obtained at different instances in time. Forexample, images can be compared to or subtracted from a reference imageobtained at another time. Such reference image, which is subtracted fromother later obtained images, may be referred to as a temporal referenceimage. This solution can be applied to spectral difference images aswell. For example, the image data resulting from spectral differenceimages can be normalized by the data corresponding to a temporalreference image. For instance, the temporal reference images can besubtracted from the spectral difference image to obtain the temporaldifference image. This process is referred to, for the purposes of thisdisclosure, as a temporal differencing algorithm or method and theresultant image from subtracting the temporal reference image fromanother image (such as the spectral difference image) is referred to asthe temporal difference image. In some embodiments where spectraldifferencing is employed, a temporal reference image may be formed, forexample, by creating a spectral difference image from the two or moreimages registered by the two or more FPAs at a single instance in time.This spectral difference image is then used as a temporal referenceimage. The temporal reference image can then be subtracted from otherlater obtained images to provide normalization that can be useful insubtracting out or removing various errors or deleterious effects. Forexample, the result of the algorithm is not affected by a priorknowledge of whether the object or scene contains a target species (suchas gas of interest), because the algorithm can highlight changes in thescene characteristics. Thus, a spectral difference image can becalculated from multiple spectral channels as discussed above based on asnap-shot image acquisition at any later time and can be subtracted fromthe temporal reference image to form a temporal difference image. Thistemporal difference image is thus a normalized difference image. Thedifference between the two images (the temporal difference image) canhighlight the target species (gas) within the normalized differenceimage, since this species was not present in the temporal referenceframe. In various embodiments, more than two FPAs can be used both forregistering the temporal reference image and a later-acquired differenceimage to obtain a better SNR figure of merit. For example, if two FPAsare associated with spectral filters having the same spectralcharacteristic, then the images obtained by the two FPAs can be combinedafter they have been registered to get a better SNR figure.

While the temporal differencing method can be used to reduce oreliminate some of the shortcomings of the spectral differencing, it canintroduce unwanted problems of its own. For example, temporaldifferencing of imaging data is less sensitive to calibration andparallax induced errors than the spectral differencing of imaging data.However, any change in the imaged scene that is not related to thetarget species of interest (such as particular gas, for example) ishighlighted in a temporally-differenced image. Thus such change in theimaged scene may be erroneously perceived as a location of the targetspecies triggering, therefore, an error in detection of target species.For example, if the temperature of the background against which the gasis being detected changes (due to natural cooling down as the dayprogresses, or increases due to a person or animal or another objectpassing through the FOV of the IR imaging system), then such temperaturechange produces a signal difference as compared to the measurement takenearlier in time. Accordingly, the cause of the scenic temperature change(the cooling object, the person walking, etc.) may appear as thedetected target species (such as gas). It follows, therefore, that anattempt to compensate for operational differences among the individualFPAs of a multi-FPA IR imaging system with the use of methods that turnon spectral or temporal differencing can cause additional problemsleading to false detection of target species. Among these problems arescene-motion-induced detection errors and parallax-caused errors thatare not readily correctable and/or compensatable. Accordingly, there isa need to compensate for image data acquisition and processing errorscaused by motion of elements within the scene being imaged. Variousembodiments of data processing algorithms described herein address andfulfill the need to compensate for such motion-induced andparallax-induced image detection errors.

In particular, to reduce or minimize parallax-induced differencesbetween the images produced with two or more predetermined FPAs, anotherdifference image can be used that is formed from the images of at leasttwo different FPAs to estimate parallax effects. Parallax error can bedetermined by comparing the images from two different FPAs where theposition between the FPAs is known. The parallax can be calculated fromthe known relative position difference. Differences between the imagesfrom these two FPAs can be attributed to parallax, especially, if theFPA have the same spectral characteristics, for example have the samespectral filter or both have no spectral filters. Parallax errorcorrection, however, can still be obtained from two FPAs that havedifferent spectral characteristics or spectral filters, especially ifthe different spectral characteristics, e.g., the transmission spectraof the respective filters are known and/or negligible. Use of more thantwo FPAs or FPAs of different locations such as FPAs spaced fartherapart can be useful. For example, when the spectral differencing of theimage data is performed with the use of the difference between theimages collected by the outermost two cameras in the array (such as, forexample, the FPAs corresponding to filters 2 and 3 of the array offilters of FIG. 5A), a difference image referred to as a “differenceimage 2-3” is formed. In this case, the alternative “difference image1-4” is additionally formed from the image data acquired by, forexample, the alternative FPAs corresponding to filters 1 and 4 of FIG.5A. Assuming or ensuring that both of these two alternative FPAs haveapproximately the same spectral sensitivity to the target species, thealternative “difference image 1-4” will highlight pixels correspondingto parallax-induced features in the image. Accordingly, based onpositive determination that the same pixels are highlighted in thespectral “difference image 2-3” used for target species detection, aconclusion can be made that the image features corresponding to thesepixels are likely to be induced by parallax and not the presence oftarget species in the imaged scene. It should be noted that compensationof parallax can also be performed using images created by individualre-imaging lenses, 128 a, when using a single FPA or multiple FPA's asdiscussed above. FPAs spaced apart from each other in differentdirections can also be useful. Greater than 2, for example, 3 or 4, ormore FPAs can be used to establish parallax for parallax correction. Incertain embodiments two central FPAs and one corner FPA are used forparallax correction. These FPA may, in certain embodiments, havesubstantially similar or the same spectral characteristics, for example,have filters having similar or the same transmission spectrum or have nofilter at all.

Another capability of the embodiments described herein is the ability toperform the volumetric estimation of a gas cloud. This can beaccomplished by using (instead of compensating or negating) the parallaxinduced effects described above. In this case, the measured parallaxbetween two or more similar spectral response images (e.g., two or morechannels or FPAs) can be used to estimate a distance between the imagingsystem and the gas cloud or between the imaging system and an object inthe field of view of the system. The parallax induced transverse imageshift, d, between two images is related to the distance, z, between thecloud or object 110 and the imaging system according to the equationz=−sz′/d. Here, s, is the separation between two similar spectralresponse images, and z′ is the distance to the image plane from the backlens. The value for z′ is typically approximately equal to the focallength f of the lens of the imaging system. Once the distance z betweenthe cloud and the imaging system is calculated, the size of the gascloud can be determined based on the magnification, m=f/z, where eachimage pixel on the gas cloud, Δx′, corresponds to a physical size inobject space Δx=Δx′/m. To estimate the volume of the gas cloud, aparticular symmetry in the thickness of the cloud based on the physicalsize of the cloud can be assumed. For example, the cloud image can berotated about a central axis running through the cloud image to create athree dimensional volume estimate of the gas cloud size. It is worthnoting that in the embodiments described herein only a single imagingsystem is required for such volume estimation. Indeed, due to the factthat the information about the angle at which the gas cloud is seen bythe system is decoded in the parallax effect, the image data includesthe information about the imaged scene viewed by the system inassociation with at least two angles.

When the temporal differencing algorithm is used for processing theacquired imaging data, a change in the scene that is not caused by thetarget species can inadvertently be highlighted in the resulting image.In various embodiments, compensation for this error makes use of thetemporal differencing between two FPAs that are substantially equallyspectrally sensitive to the target species. In this case, the temporaldifference image will highlight those pixels the intensity of which havechanged in time (and not in wavelength). Therefore, subtracting the datacorresponding to these pixels on both FPAs, which are substantiallyequally spectrally sensitive to the target species, to form theresulting image, excludes the contribution of the target species to theresulting image. The differentiation between (i) changes in the scenedue to the presence of target species and (ii) changes in the scenecaused by changes in the background not associated with the targetspecies is, therefore, possible. In some embodiments, these two channelshaving the same or substantially similar spectral response so as to besubstantially equally spectrally sensitive to the target species maycomprise FPAs that operate using visible light. It should also be notedthat, the data acquired with a visible light FPA (when present as partof the otherwise IR imaging system) can also be used to facilitate suchdifferentiation and compensation of the motion-caused imaging errors.Visible cameras generally have much lower noise figure than IR cameras(at least during daytime). Consequently, the temporal difference imageobtained with the use of image data from the visible light FPA can bequite accurate. The visible FPA can be used to compensate for motion inthe system as well as many potential false-alarms in the scene due tomotion caused by people, vehicles, birds, and steam, for example, aslong as the moving object can be observed in the visible region of thespectra. This has the added benefit of providing an additional level offalse alarm suppression without reducing the sensitivity of the systemsince many targets such as gas clouds cannot be observed in the visiblespectral region. In various implementations, an IR camera can be used tocompensate for motion artifacts.

Another method for detection of the gases is to use a spectral unmixingapproach. A spectral unmixing approach assumes that the spectrummeasured at a detector pixel is composed of a sum of component spectra(e.g., methane and other gases). This approach attempts to estimate therelative weights of these components needed to derive the measurementspectrum. The component spectra are generally taken from a predeterminedspectral library (for example, from data collection that has beenempirically assembled), though sometimes one can use the scene toestimate these as well (often called “endmember determination”). Invarious embodiments, the image obtained by the detector pixel is aradiance spectrum and provides information about the brightness of theobject. To identify the contents of a gas cloud in the scene and/or toestimate the concentration of the various gases in the gas cloud, anabsorption/emission spectrum of the various gases of interest can beobtained by comparing the measured brightness with an estimate of theexpected brightness. The spectral unmixing methodology can also benefitfrom temporal, parallax, and motion compensation techniques.

In various embodiments, a method of identifying the presence of a targetspecies in the object includes obtaining the radiance spectrum (or theabsorption spectrum) from the object in a spectral region indicative ofthe presence of the target species and calculating a correlation (e.g.,a correlation coefficient) by correlating the obtained radiance spectrum(or the absorption spectrum) with a reference spectrum for the targetspecies. The presence or absence of the target species can be determinedbased on an amount of correlation (e.g., a value of correlationcoefficient). For example, the presence of the target species in theobject can be confirmed if the amount of correlation or the value ofcorrelation coefficient is greater than a threshold. In variousimplementations, the radiance spectrum (or the absorption spectrum) canbe obtained by obtaining a spectral difference image between a filteredoptical channel and/or another filtered optical channel/unfilteredoptical channel or any combinations thereof.

For example, an embodiment of the system configured to detect thepresence of methane in a gas cloud comprises optical components suchthat one or more of the plurality of optical channels is configured tocollect IR radiation to provide spectral data corresponding to adiscrete spectral band located in the wavelength range between about 7.9μm and about 8.4 μm corresponding to an absorption peak of methane. Themultispectral data obtained in the one or more optical channels can becorrelated with a predetermined absorption spectrum of methane in thewavelength range between about 7.9 μm and 8.4 μm. In variousimplementations, the predetermined absorption spectrum of methane can besaved in a database or a reference library accessible by the system.Based on an amount of correlation (e.g., a value of correlationcoefficient), the presence or absence of methane in the gas cloud can bedetected.

Examples of Practical Embodiments and Operation

The embodiment 300 of FIG. 3 is configured to employ 12 optical channelsand 12 corresponding microbolometer FPAs 336 to capture a video sequencesubstantially immediately after performing calibration measurements. Thevideo sequence corresponds to images of a standard laboratory scene andthe calibration measurements are performed with the use of a referencesource including two shutters, as discussed above, one at roomtemperature and one 5° C. above room temperature. The use of 12 FPAsallows increased chance of simultaneous detection and estimation of theconcentrations of about 8 or 9 gases present at the scene. In variousembodiments, the number of FPAs 336 can vary, depending on the balancebetween the operational requirements and consideration of cost.

Due to the specifics of operation in the IR range of the spectrum, theuse of the so-called noise-equivalent temperature difference (or NETD)is preferred and is analogous to the SNR commonly used in visiblespectrum instruments. The array of microbolometer FPAs 336 ischaracterized to perform at NETD≦72 mK at an f-number of 1.2. Eachmeasurement was carried out by summing four consecutive frames, and thereduction in the NETD value expected due to such summation would bedescribed by corresponding factor of √4=2. Under ideal measurementconditions, therefore, the FPA NETD should be about 36 mK.

It is worth noting that the use of optically-filtered FPAs in variousembodiments of the system described herein can provide a system withhigher number of pixels. For example, embodiments including a singlelarge format microbolometer FPA array can provide a system with largenumber of pixels. Various embodiments of the systems described hereincan also offer a high optical throughput for a substantially low numberof optical channels. For example, the systems described herein canprovide a high optical throughput for a number of optical channelsbetween 4 and 50. By having a lower number of optical channels (e.g.,between 4 and 50 optical channels), the systems described herein havewider spectral bins which allows the signals acquired within eachspectral bin to have a greater integrated intensity.

An advantage of the embodiments described herein over various scanningbased hyperspectral systems that are configured for target speciesdetection (for example, gas cloud detection) is that, the entirespectrum can be resolved in a snapshot mode (for example, during oneimage frame acquisition by the FPA array). This feature enables theembodiments of the imaging systems described herein to take advantage ofthe compensation algorithms such as the parallax and motion compensationalgorithms mentioned above. Indeed, as the imaging data required toimplement these algorithms are collected simultaneously with thetarget-species related data, the compensation algorithms are carried outwith respect to target-species related data and not with respect to dataacquired at another time interval. This rapid data collection thusimproves the accuracy of the data compensation process. In addition, theframe rate of data acquisition is much higher. For example, embodimentsof the imaging system described herein can operate at video rates fromabout 5 Hz and higher. For example, various embodiments described hereincan operate at frame rates from about 5 Hz to about 60 Hz or 200 Hz.Thus, the user is able to recognize in the images the wisps and swirlstypical of gas mixing without blurring out of these dynamic imagefeatures and other artifacts caused by the change of scene (whetherspatial or spectral) during the lengthy measurements. Incontradistinction, scanning based imaging systems involve image dataacquisition over a period of time exceeding a single-snap-shot time andcan, therefore, blur the target gas features in the image and inevitablyreduce the otherwise achievable sensitivity of the detection. Thisresult is in contrast to embodiments of the imaging system describedherein that are capable of detecting the localized concentrations of gaswithout it being smeared out with the areas of thinner gasconcentrations. In addition, the higher frame rate also enables a muchfaster response rate to a leak of gas (when detecting such leak is thegoal). For example, an alarm can trigger within fractions of a secondrather than several seconds.

To demonstrate the operation and gas detection capability of the imagingsystems described herein, a prototype was constructed in accordance withthe embodiment 300 of FIG. 3A and used to detect a hydrocarbon gas cloudof propylene at a distance of approximately 10 feet. FIG. 7 illustratesvideo frames 1 through 12 representing gas-cloud-detection output 710(seen as a streak of light) in a sequence from t=1 to t=12. The images 1through 12 are selected frames taken from a video-data sequence capturedat a video-rate of 15 frames/sec. The detected propylene gas is shown asa streak of light 710 (highlighted in red) near the center of eachimage. The first image is taken just prior to the gas emerging from thenozzle of a gas-contained, while the last image represents the systemoutput shortly after the nozzle has been turned off.

The same prototype of the system can also demonstrate the dynamiccalibration improvement described above by imaging the scene surroundingthe system (the laboratory) with known temperature differences. Theresult of implementing the dynamic correction procedure is shown inFIGS. 8A, 8B, where the curves labeled “obj” (or “A”) representtemperature estimates of an identified region in the scene. The abscissain each of the plots of FIGS. 8A, 8B indicates the number of a FPA,while the ordinate corresponds to temperature (in degrees C.).Accordingly, it is expected that when all detector elements receiveradiant data that, when interpreted as the object's temperature,indicates that the object's temperature perceived by all detectorelements is the same, any given curve would be a substantially flatline. Data corresponding to each of the multiple “obj” curves are takenfrom a stream of video frames separated from one another by about 0.5seconds (for a total of 50 frames). The recorded “obj” curves shown inFIG. 8A indicate that the detector elements disagree about the object'stemperature, and that difference in object's temperature perceived bydifferent detector elements is as high as about 2.5° C. In addition, allof the temperature estimates are steadily drifting in time, from frameto frame. The curves labeled “ref” (or “C”) correspond to the detectors'estimates of the temperature of the aperture 338 of the embodiment 300of FIG. 3A. The results of detection of radiation carried out after eachdetector pixel has been subjected to the dynamic calibration proceduredescribed above are expressed with the curved labeled “obj con” (or“B”). Now, the difference in estimated temperature of the object amongthe detector elements is reduced to about 0.5° C. (thereby improving theoriginal reading at least by a factor of 5).

FIG. 8B represents the results of similar measurements corresponding toa different location in the scene (a location which is at a temperatureabout 9° C. above the estimated temperature of the aperture 338 of FIG.3A). As shown, the correction algorithm discussed above is operable andeffective and applicable to objects kept at different temperature.Accordingly, the algorithm is substantially temperature independent.

Dynamic Calibration Elements and References

FIGS. 9A and 9B illustrates schematically different implementations 900and 905 respectively of the imaging system that include a variety oftemperature calibration elements to facilitate dynamic calibration ofthe FPAs. The temperature calibration elements can include mirrors 975a, 975 b (represented as M_(1A), M_(9A), etc.) as well as referencesources 972 a and 972 b. The implementation 900 can be similarlyconfigured as the embodiment 300 and include one or more front objectivelens, a divided aperture, one or more spectral filters, an array ofimaging lenses 928 a and an imaging element 936. In variousimplementations, the imaging element 936 (e.g., camera block) caninclude an array of cameras. In various implementations, the array ofcameras can comprise an optical FPA unit. The optical FPA unit cancomprise a single FPA, an array of FPAs. In various implementations, thearray of cameras can include one or more detector arrays represented asdetector array 1, detector array 5, detector array 9 in FIGS. 9A and 9B.In various embodiments, the FOV of each of the detector arrays 1, 5, 9can be divided into a central region and a peripheral region. Withoutany loss of generality, the central region of the FOV of each of thedetector arrays 1, 5, 9 can include the region where the FOV of all thedetector arrays 1, 5, 9 overlap. In the embodiment illustrated in FIG.9A, the reference sources 972 a and 972 b are placed at a distance fromthe detector arrays 1, 5, 9, for example, and mirrors 975 a and 975 bthat can image them onto the detector arrays are then placed at thelocation of the scene reference aperture (e.g., 338 of FIG. 3A).

In FIG. 9A, the mirrors 975 a and 975 b are configured to reflectradiation from the reference sources 972 a and 972 b (represented as refA and ref B). The mirrors 975 a and 975 b can be disposed away from thecentral FOV of the detector arrays 1, 5, 9 such that the central FOV isnot blocked or obscured by the image of the reference source 972 a and972 b. In various implementations, the FOV of the detector array 5 couldbe greater than the FOV of the detector arrays 1 and 9. In suchimplementations, the mirrors 975 a and 975 b can be disposed away fromthe central FOV of the detector array 5 at a location such that thereference source 972 a and 972 b is imaged by the detector array 5. Themirrors 975 a and 975 b may comprise imaging optical elements havingoptical power that image the reference sources 972 a and 972 b onto thedetector arrays 1 and 9. In this example, the reference sources 972 aand 972 b can be disposed in the same plane as the re-imaging lenses 928a, however, the reference sources 972 a and 972 b can be disposed in adifferent plane or in different locations. For example, the referencesources 972 a and 972 b can be disposed in a plane that is conjugate tothe plane in which the detector array 1, detector array 5, and detectorarray 9 are disposed such that a focused image of the reference sources972 a and 972 b is formed by the detector arrays. In someimplementations, the reference sources 972 a and 972 b can be disposedin a plane that is spaced apart from the conjugate plane such that adefocused image of the reference sources 972 a and 972 b is formed bythe detector arrays. In various implementations, the reference sources972 a and 972 b need not be disposed in the same plane.

As discussed above, in some embodiments, the reference sources 972 a and972 b are imaged onto the detector array 1 and detector array 9, withoutmuch blur such that the reference sources 972 a and 972 b are focused.In contrast, in other embodiments, the image of reference sources 972 aand 972 b formed on the detector array 1, and detector array 9 areblurred such that the reference sources 972 a and 972 b are defocused,and thereby provide some averaging, smoothing, and/or low passfiltering. The reference sources 972 a and 972 b may comprise a surfaceof known temperature and may or may not include a heater or coolerattached thereto or in thermal communication therewith. For example, thereference source 972 a and 972 b may comprises heaters and coolersrespectively or may comprise a surface with a temperature sensor and aheater and sensor respectively in direct thermal communication therewithto control the temperature of the reference surface. In variousimplementations, the reference sources 972 a and 972 b can include atemperature controller configured to maintain the reference sources 972a and 972 b at a known temperature. In some implementations, thereference sources 972 a and 972 b can be associated with one or moresensors that measure the temperature of the reference sources 972 a and972 b and communicate the measured temperature to the temperaturecontroller. In some implementations, the one or more sensors cancommunicate the measured temperature to the data-processing unit. Invarious implementations, the reference sources 972 a and 972 b maycomprise a surface of unknown temperature. For example, the referencesources may comprise a wall of a housing comprising the imaging system.In some implementations, the reference sources 972 a and 972 b cancomprise a surface that need not be associated with sensors, temperaturecontrollers. However, in other implementations, the reference sources972 a and 972 b can comprise a surface that can be associated withsensors, temperature controllers.

In FIG. 9B, the temperature-calibration elements comprisetemperature-controlled elements 972 a and 972 b (e.g., a thermallycontrolled emitter, a heating strip, a heater or a cooler) disposed adistance from the detector arrays 1, 5, 9. In various embodiments, thetemperature-controlled elements 972 a and 972 b can be disposed awayfrom the central FOV of the detector arrays 1, 5, 9 such that thecentral FOV is not blocked or obscured by the image of the referencesource 972 a and 972 b. The radiation emitted from the reference sources972 a and 972 b is also imaged by the detector array 936 along with theradiation incident from the object. Depending on the position of thereference sources 972 a and 972 b the image obtained by the detectorarray of the reference sources can be blurred (or defocused) or sharp(or focused). The images 980 a, 980 b, 980 c, 980 d, 980 e and 980 f ofthe temperature-controlled elements 972 a and 972 b can be used as areference to dynamically calibrate the one or more cameras in the arrayof cameras.

In the implementations depicted in FIGS. 9A and 9B, the detector arrays1, 5 and 9 are configured to view (or image) both the reference sources972 a and 972 b. Accordingly, multiple frames (e.g., every orsubstantially every frame) within a sequence of images contains one ormore regions in the image in which the object image has known thermaland spectral properties. This allows multiple (e.g., most or each)cameras within the array of cameras to be calibrated to agree with other(e.g., most or every other) camera imaging the same reference source(s)or surface(s). For example, detector arrays 1 and 9 can be calibrated toagree with each other. As another example, detector arrays 1, 5 and 9can be calibrated to agree with each other. In various embodiments, thelenses 928 a provide blurred (or defocused) images of the referencesources 972 a, 972 b on the detector arrays 1 and 9 because the locationof the reference sources are not exactly in a conjugate planes of thedetector arrays 1 and 9. Although the lenses 928 a are described asproviding blurred or defocused images, in various embodiments, referencesources or surfaces are imaged on the detectors arrays 1, 5, 9 withoutsuch blur and defocus and instead are focused images. Additionallyoptical elements may be used, such as for example, the mirrors shown inFIG. 9A to provide such focused images.

The temperature of the reference sources 972 b, 972 a can be different.For example, the reference source 972 a can be at a temperature T_(A),and the reference source 972 b can be at a temperature T_(B) lower thanthe temperature T_(A). A heater can be provided under thetemperature-controlled element 972 a to maintain it at a temperatureT_(A), and a cooler can be provided underneath thetemperature-controlled element 972 b to maintain it at a temperatureT_(B). In various implementations, the embodiments illustrated in FIGS.9A and 9B can be configured to image a single reference source 972instead of two references sources 972 a and 972 b maintained atdifferent temperatures. It is understood that the single referencesource need not be thermally controlled. For example, in variousimplementations, a plurality of detectors in the detector array can beconfigured to image a same surface of at least one calibration elementwhose thermal and spectral properties are unknown. In suchimplementations, one of the plurality of detectors can be configured asa reference detector and the temperature of the surface of the at leastone calibration element imaged by the plurality of detectors can beestimated using the radiance spectrum obtained by the referencedetector. The remaining plurality of detectors can be calibrated suchthat their temperature and/or spectral measurements agree with thereference detector. For example, detector arrays 1 and 9 can becalibrated to agree with each other. As another example, detector arrays1, 5 and 9 can be calibrated to agree with each other.

The reference sources 972 a and 972 b can be coated with a material tomake it behave substantially as a blackbody (for which the emissionspectrum is known for any given temperature). If a temperature sensor isused at the location of each reference source, then the temperature canbe tracked at these locations. As a result, the regions in the image ofeach camera (e.g., on the detector arrays 1 and 9) in which the objecthas such known temperature (and, therefore, spectrum) can be defined. Acalibration procedure can thus be used so that most of the cameras (ifnot every camera) so operated agrees, operationally, with most or everyother camera, for objects at the temperatures represented by those twosources. Calibrating infrared cameras using sources at two differenttemperatures is known as a “two-point” calibration, and assumes that themeasured signal at a given pixel is linearly related to the incidentirradiance. Since this calibration can be performed during multiple,more, or even every frame of a sequence, it is referred to as a “dynamiccalibration”.

An example of the dynamic calibration procedure is as follows. If thereis a temperature sensor on the reference sources or reference surface,then the temperature measurements obtained by these temperature sensorscan be used to determine their expected emission spectra. Thesetemperature measurements are labeled as T_(A)[R], T_(B)[R], and T_(C)[R]for the “reference temperatures” of sources/surfaces A, B, and C. Thesetemperature measurements can be used as scalar correction factors toapply to the entire image of a given camera, forcing it to agree withthe reference temperatures. Correcting the temperature estimate of agiven pixel from T to T′ can use formulae analogous to those discussedbelow in reference to FIGS. 10A, 10B, 10C. If no direct temperaturesensor is used, then one of the cameras can be used instead. This cameracan be referred to as the “reference camera”. In this case, the sameformulae as those provided in paragraph below can be used, but withT_(A)[R] and T_(B)[R] representing the temperatures of the referencesources/surfaces A and B as estimated by the reference camera. Byapplying the dynamic calibration correction formulae, all of the othercameras are forced to match the temperature estimates of the referencecamera.

In the configuration illustrated in FIG. 9B, the reference sources 972 aand 972 b are placed such that the images of the sources on the detectorarrays are blurred. The configuration illustrated in FIG. 9A is similarto the system 400 illustrated in FIG. 4 where the reference sources areplaced at an intermediate image plane (e.g., a conjugate image plane).In this configuration, the array of reference apertures, similar toreference apertures 438 a in FIG. 4, will have an accompanying array ofreference sources or reference surfaces such that the reference sourcesor surfaces (e.g., each reference source or surface) are imaged onto acamera or a detector array such as FPAs 1, 5, 9. With this approach, thereference source or surface images are at a conjugate image plane andthus are not appreciably blurred, so that their images can be made toblock a smaller portion of each camera's field of view.

A “static” calibration (a procedure in which the scene is largelyblocked with a reference source such as the moving shutters 960 in FIGS.9A and 9B, so that imaging of an unknown scene cannot be performed inparallel with calibration) allows a plurality of the cameras (forexample, most or each camera) to accurately estimate the temperature ofa plurality of elements (for example, most or each element in the scene)immediately after the calibration is complete. It cannot, however,prevent the cameras' estimates from drifting away from one anotherduring the process of imaging an unknown scene. The dynamic calibrationcan be used to reduce or prevent this drift, so that all cameras imaginga scene can be forced to agree on the temperature estimate of thereference sources/surfaces, and adjust this correction during everyframe.

FIG. 10A illustrates schematically a related embodiment 1000 of theimaging system, in which one or more mirrors M_(0A), . . . M_(11A) andM_(0B), . . . M_(11B) are placed within the fields of view of one ormore cameras 0, . . . , 11, partially blocking the field of view. Thecameras 0, . . . , 11 are arranged to form an outer ring of camerasincluding cameras 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4 surrounding thecentral cameras 5 and 6. In various implementations, the FOV of thecentral cameras 5 and 6 can be less than or equal to the FOV of theouter ring of cameras 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4. In suchimplementations, the one or more mirrors M_(0A), . . . M_(11A) andM_(0B), . . . M_(11B) can be placed outside the central FOV of thecameras 5 and 6 and is placed in a peripheral FOV of the cameras outerring of cameras 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4 which does not overlapwith the central FOV of the cameras 5 and 6 such that the referencesources A and B are not imaged by the cameras 5 and 6. In variousimplementations, the FOV of the central cameras 5 and 6 can be greaterthan the FOV of the outer ring of cameras 0, 1, 2, 3, 7, 11, 10, 9, 8and 4. In such implementations, the one or more mirrors M_(0A), . . .M_(11A) and M_(0B), . . . M_(11B) can be placed in a peripheral FOV ofthe cameras 5 and 6 which does overlap with the central FOV of the outerring of cameras 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4 such that thereference sources A and B are imaged by the cameras 5 and 6.

This design is an enhancement to the systems 300 and 400 shown in FIGS.3A and 4A. In the system 1000 shown in FIG. 10A, an array of two or moreimaging elements (curved mirrors, for example) is installed at adistance from the FPAs, for example, in the plane of the referenceaperture 160 shown in FIG. 3A. These elements (mirror or imagingelements) are used to image one or more temperature-controlled referencesources A and B onto the detector elements of two or more of thecameras. The primary difference between embodiment 1000 and embodiment300 or 400 is that now a plurality or most or all of the outer ring ofcameras in the array can image both the reference sources A and Binstead of imaging one of the two reference source A and B. Accordingly,most or all of the outer ring of cameras image an identical referencesource or an identical set of reference sources (e.g., both thereference sources A and B) rather than using different reference sourcesfor different cameras or imaging different portions of the referencesources as shown in FIGS. 3A and 4A. Thus, this approach improves therobustness of the calibration, as it eliminates potential failures anderrors due to the having additional thermal sensors estimating eachreference source.

The imaging elements in the system 1000 (shown as mirrors in FIGS. 10Aand 10B) image one or more controlled-temperature reference sources or asurface of a calibration element (shown as A and B in FIGS. 10A and 10B)into the blocked region of the cameras' fields of view. FIG. 10B showsan example in which mirror M_(0A) images reference source/surface A ontocamera 0, and mirror M_(0B) images reference source/surface B ontocamera 0, and likewise for cameras 1, 2, and 3. This way, each of themirrors is used to image a reference source/surface onto a detectorarray of a camera, so that many, most, or every frame within a sequenceof images contains one or more regions in the image in which the objectimage has known thermal and spectral properties. This approach allowsmost of the camera, if not each camera, within the array of cameras tobe calibrated to agree with most or every other camera imaging the samereference source or sources. For example, cameras 0, 1, 2, 3, 7, 11, 10,9, 8 and 4 can be calibrated to agree with each other. As anotherexample, cameras 0, 1, 2 and 3 can be calibrated to agree with eachother. As yet another example, cameras 0, 1, 2, 3, 7, 11, 10, 9, 8, 4, 5and 6 can be calibrated to agree with each other. Accordingly, invarious implementations, two, three, four, five, six, seven, eight,nine, ten, eleven or twelve cameras can be calibrated to agree with eachother. In certain embodiments, however, not all the cameras arecalibrated to agree with each other. For example, one, two, or morecameras may not be calibrated to agree with each other while others maybe calibrated to agree with each other. In various embodiments, thesemirrors may be configured to image the reference sources/surfaces A andB onto different respective pixels a given FPA. Without any loss ofgenerality, FIGS. 10A and 10B represent a top view of the embodimentshown in FIG. 9A.

FIG. 10C illustrates schematically a related embodiment 1050 of theimaging system, in which one or more′ reference sources R_(0A), . . . ,R_(11A) and R_(0B), . . . , R_(11B) are disposed around the array ofdetectors 0, . . . , 11. In various implementations, the one or morereference sources R_(0A), . . . , R_(11A) and R_(0B), . . . , R_(11B)can be a single reference source that is imaged by the detectors 0, . .. , 11. In various implementations, central detector arrays 5 and 6 canhave a FOV that is equal to or lesser than the FOV of the outer ring ofthe detectors 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4. In suchimplementations, the reference sources R_(0A), . . . , R_(11A) can bedisposed away from the central FOV of the detector arrays 5 and 6 suchthat the radiation from the reference sources R_(0A), . . . , R_(11A) isimaged only by the outer ring of detectors 0, 1, 2, 3, 7, 11, 10, 9, 8and 4. In various implementations, central detector arrays 5 and 6 canhave a FOV that is greater than the FOV of the outer ring of thedetectors 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4. In such implementations,the reference sources R_(0A), . . . , R_(11A) can be disposed in theperipheral FOV of the detector arrays 5 and 6 such that the radiationfrom the reference sources R_(0A), . . . , R_(11A) is imaged only by theouter ring of detectors 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4. The radiationfrom the reference sources R_(0A), . . . , R_(11A) is therefore imagedby the outer ring of detectors 0, 1, 2, 3, 7, 11, 10, 9, 8 and 4 as wellas central cameras 5 and 6. Without any loss of generality, FIG. 10Crepresents a top view of the embodiment shown in FIG. 9B.

In various implementations, a heater can be provided underneath,adjacent to, or in thermal communication with reference source/surface Ato give it a higher temperature T_(A), and a cooler can be providedunderneath, adjacent to, or in thermal communication with referencesource B to give it a lower temperature T_(B). In variousimplementations, the embodiments illustrated in FIGS. 10A, 10B and 10Ccan be configured to image a single reference source A instead of tworeferences sources A and B maintained at different temperatures. Asdiscussed above, the embodiments illustrated in FIGS. 10A, 10B and 10Ccan be configured to image a same surface of a calibration element. Insuch implementations, the temperature of the surface of the calibrationelement need not be known. Many, most or each reference source/surfacecan be coated with a material to make it behave approximately as ablackbody, for which the emission spectrum is known for any giventemperature. If many, most, or each camera in the array of camerasimages both of references A and B, so that there are known regions inthe image of these cameras in which the object has a known temperature(and therefore spectrum), then one can perform a calibration procedure.This procedure can provide that many, most or every camera so operatedagrees with various, most, or every other camera, for objects at thetemperatures represented by those two sources. For example, two, three,four, five, six, seven, eight, nine, ten, eleven or twelve cameras canbe calibrated to agree with each other. In certain embodiments, however,not all the cameras are calibrated to agree with each other. Forexample, one, two, or more cameras may not be calibrated to agree witheach other while others may be calibrated to agree with each other. Asdiscussed above, calibration of infrared cameras using sources at twodifferent temperatures is known as a “two-point” calibration, andassumes that the measured signal at a given pixel is linearly related tothe incident irradiance.

The dynamic calibration is used to obtain a corrected temperature T′from the initial temperature T estimated at each pixel in a camera usingthe following formulae:

T′[x,y,c]=(T[x,y,c]−T _(A) [R])G[c]+T _(A) [R]

where is T_(A)[R] is a dynamic offset correction factor, and,

${{G\lbrack c\rbrack} = \frac{{T_{B}\lbrack R\rbrack} - {T_{A}\lbrack R\rbrack}}{{T_{B}\lbrack c\rbrack} - {T_{A}\lbrack c\rbrack}}},$

is a dynamic gain correction factor. The term c discussed above is acamera index that identifies the camera whose data is being corrected.

III. Examples of a Mobile DAISI System

The DAISI systems disclosed herein can be configured to be installed ata suitable location on a long-term basis, according to some embodiments.For example, the DAISI systems disclosed in Section II above can beaffixed to a fixture mounted to the ground at a location to continuouslyor periodically monitor the presence of gases or chemicals at thelocation. In some embodiments, for example, the DAISI systems can beattached to a pole, post, or any suitable fixture at the location to bemonitored. In such arrangements, the DAISI system can continuously orperiodically capture multispectral, multiplexed image data of the scene,and an on-board or remote computing unit can process the captured imagedata to identify or characterize gases or chemicals at the location. Acommunications module can communicate data relating to the identifiedgases or chemicals to any suitable external system, such as a centralcomputing server, etc. For such long-term installations of the DAISIsystem, the installation site may include a power source (e.g.,electrical transmission lines connected to a junction box at the site)and network communications equipment (e.g., network wiring, routers,etc.) to provide network communication between the DAISI system and theexternal systems.

It can be advantageous to provide a mobile DAISI system configured to beworn or carried by a user. For example, it may be unsuitable orundesirable to install a DAISI system at some locations on a long-termbasis. As an example, some oil well sites may not have sufficientinfrastructure, such as power sources or network communicationequipment, to support the DAISI system. In addition, it can bechallenging to move the DAISI system from site to site to monitordifferent locations. For example, installing and removing the DAISIsystem from a site for transport may involve substantial effort and timefor the user when the system is connected to infrastructure at the siteto be monitored. Accordingly, it can be desirable to provide a DAISIsystem that can be used independently of the facilities orinfrastructure at the site to be monitored. Furthermore, it can beadvantageous to implement the DAISI system in a form factor and with aweight that can be carried or worn by a user. For example, a mobileDAISI system can enable the user to easily transport the system fromsite-to-site, while monitoring the presence of gases or chemicals inreal-time.

It should be appreciated that each of the systems disclosed herein canbe used to monitor potential gas leaks in any suitable installationsite, including, without limitation, drilling rigs, refineries,pipelines, transportations systems, ships or other vessels (such asoff-shore oil rigs, trains, tanker trucks, petro-chemical plants,chemical plants, etc. In addition, each of the embodiments and aspectsdisclosed and illustrated herein such as above, e.g., with respect toFIGS. 1-10C, can be used in combination with each of the embodimentsdisclosed and illustrated herein with respect to FIGS. 11A-14C.

FIG. 11A is a schematic diagram illustrating a mobile infrared imagingsystem 1000 (e.g., a mobile or portable DAISI system) configured to becarried or worn by a human user 1275. The user 1275 may wear a hat orhelmet 1200 when he travels to a site to be monitored, such as an oilwell site, a refinery, etc. The system 1000 shown in FIG. 11A isattached to the helmet 1200 by way of a support 1204 that securelymounts the system 1000 to the helmet 1200. For example, the support 1204can comprise a fastener, a strap, or any other suitable structure.Advantageously, mounting the system 1000 to the helmet 1200 can enablethe user 1275 to capture images within the system's field of view (FOV)by turning his head to face a particular location to be monitored. Forexample, the user 1275 can walk through the site and can capture videoimages of each portion of the site, e.g., various structures that may besusceptible to gas or chemical leaks, such as valves, fittings, etc.Thus, in the embodiment shown in FIG. 11A, the user 1275 can image eachportion of the site by facing the area to be imaged and ensuring thatthe system 1000 is activated. In addition, by mounting the system 1000to the user's helmet 1200, the user 1275 may use his hands for othertasks while the system 1000 images the site. Although the system 1000 ofFIG. 11A is shown as being mounted to the user's helmet 1200, it shouldbe appreciated that the system 1000 can instead be worn on other partsof the user's clothing or can be carried by the user, e.g., in a bag,case, or other suitable container. Furthermore, in some embodiments, awind sensor can be provided to the user, e.g., on the user's clothingand/or on or near the system 1000. The wind sensor can be used toestimate wind conditions at the installation site, which can be used toimprove the detection of gas leaks. In other embodiments, the system1000 can be coupled to or formed with a housing that defines a“gun”-like structure which can be aimed or pointed by the user in aparticular direction.

As explained herein, a gas cloud 1202 emitted from a structure at thesite can be imaged by pointing the system 1000 towards the gas cloud1202 and capturing an image of the gas cloud 1202 when the cloud 1202 iswithin the FOV of the system 1000. Unlike other systems, the system 1000can capture multispectral image data of a single scene over a range ofIR wavelengths with a single snapshot, as explained in further detailherein. The single snapshot can be captured in a short timeframe, e.g.,less than about 3 seconds, less than about 2 seconds, or less than about1.5 seconds (for example, in about 1 second, in some embodiments). Thesingle snapshot can be captured in greater than about 5 milliseconds,greater than about 0.2 seconds, or greater than about 0.5 seconds. Thecaptured image data can be processed on board the system 1000 by aprocessing unit, as explained in further detail herein. For example, theprocessing unit can process the image data from the different opticalchannels and can compare the captured spectral information with adatabase of known chemicals to identify and/or characterize the gasesthat are included in the gas cloud 1202.

A communications module on board the system 1000 can transmitinformation relating to the identified gases or chemicals to anysuitable external device. For example, the communications module canwirelessly communicate (e.g., by Bluetooth, WiFi, etc.) the informationto a suitable mobile computing device, such as an electronic eyewearapparatus 1201, a tablet computing device 1212, a mobile smartphone, alaptop or notebook computer 1203, or any other suitable mobile computingdevice. In some embodiments, if a gas cloud is detected, the system 1000can warn the user by way of sending a signal to the mobile device (e.g.,tablet computing device 1212 or a mobile smartphone. The mobile devicecan emit an audible ring and/or can vibrate to notify the user of apotential gas leak. In the embodiment of FIG. 11A, the electroniceyewear apparatus 1201 can include a user interface comprising a displaythat the user 1275 can view in real-time as he visits the site. In someembodiments, the electronic eyewear apparatus 1201 comprises eyewearthat includes a display. The electronics eyewear apparatus 1201 can befurther configured to present images from this display to the wearer.The electronics eyewear apparatus 1201 may for example includeprojection optics that projects the image into the eye. The electroniceyewear apparatus 1201 may comprise heads up display optics the presentsthe image on the lens portion(s) of the eyewear so that the wearer canview the image and also see through the eyewear and peer at objects inthe distance. Other configurations are possible. In some arrangements,the eyewear apparatus 1201 can comprise a Google Glass device, sold byGoogle, Inc., of Mountain View, Calif.

The processing unit can configure the processed image data such that thetypes of identified gases are displayed to the user 1275 on the displayof the eyewear apparatus 1201. For example, in some embodiments,color-coded data may represent different types of gases orconcentrations of a particular gas, and may be overlaid on a visiblelight image of the scene. For example, the color-coded data and image ofthe gas cloud can be seen by the user on the electronic eyewearapparatus 1201. In various embodiments, text data and statistics aboutthe composition of the gas cloud 1202 may also be displayed to the user1275. Thus, the user 1275 can walk the site and can view the differenttypes of gases in the gas cloud 1202 substantially in real-time.Advantageously, such real-time display of the composition of the gascloud 1202 can enable the user 1275 to quickly report urgent events,such as the leakage of a toxic gas or chemical. In some embodiments,detection of a toxic leak can trigger an alarm, which may causeemergency personnel to help evacuate the site and/or fix the leak.

In some embodiments, the processed image data can be transmitted fromthe system 1000 to the tablet computing device 1212, laptop computer1203, and/or smartphone. The user 1275 can interact with the tablecomputing device 1212 or laptop computer 1203 to conduct additionalanalysis of the imaged and processed gas cloud 1202. Furthermore,information about the gas cloud (including the processed data and/or theraw image data) may also be transmitted to a central server forcentralized collection, processing, and analysis. In variousarrangements, a global positioning system (GPS) module can also beinstalled on board the system 1000 and/or on the mobile computing device(such as a tablet computing device, smartphone, etc.). The GPS modulecan identify the coordinates of the user 1275 when a particular image iscaptured. The location data for the captured image data can be stored onthe central server for further analysis.

Thus, the system 1000 shown in FIG. 11A can enable the user 1275 toimage multiple locations of a particular site to be monitored, such asan oil well site. Advantageously, the optical components, the processingcomponents, and the communications components of the system 1000 can beintegrated within a relatively small housing that can be carried or wornby the user 1275. For example, in various embodiments, the system 1000does not include complex mechanical components for movement, such asgimbals, actuators, motors, etc. Without such components, the size ofthe system 1000 can be reduced relative to other systems.

Unlike other systems, in which the system components are bulky or areassembled over a large form factor, the mobile system 1000 can be sizedand shaped in such a manner so as to be easily moved and manipulatedwhen the user 1275 moves about the site. Indeed, it can be verychallenging to integrate the various system components in a smallform-factor. Advantageously, the systems 1000 can be worn or carried bya human user. For example, the components of the system 1000 can becontained together in a data acquisition and processing module 1020,which may include a housing to support the system components. Thecomponents of the system 1000 (including the optical or imagingcomponents, the focal plane array, the on-board processing electronics,and the communications components) may be packaged or assembled in thedata acquisition and processing module 1020 and may occupy a volume lessthan about 300 cubic inches, less than about 200 cubic inches, or lessthan about 100 cubic inches. In various embodiments, the components ofthe system 1000 (including the optical or imaging components, the focalplane array, the on-board processing electronics, and the communicationscomponents) may be packaged or assembled in the data acquisition andprocessing module 1020 and may occupy a volume greater than about 2cubic inches, or greater than about 16 cubic inches.

The data acquisition and processing module 1020 (with the systemcomponents mounted therein or thereon) may be sized and shaped to fitwithin a box-shaped boundary having dimensions X×Y× Z. For example, thedata acquisition and processing module 1020, including the imagingoptics, focal plane array, and on board processing electronics, may beincluded in a package that is sized and shaped to fit within thebox-shaped boundary having dimensions X× Y× Z. This package may alsocontain a power supply, such as a battery and/or solar module. In someembodiments, the data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can be sized and shaped to fit within a box-shapedboundary smaller than 8 inches×6 inches×6 inches. In some embodiments,the data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canbe sized and shaped to fit within a box-shaped boundary smaller than 7inches×5 inches×5 inches, e.g., a box-shaped boundary small than 7inches×3 inches×3 inches. In some embodiments, the data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can be sized and shaped to fitwithin a box-shaped boundary smaller than 6 inches×4 inches×4 inches. Insome embodiments, the data acquisition and processing module 1020(including the imaging optics, focal plane array, and on boardprocessing electronics may) can be sized and shaped to fit within abox-shaped boundary smaller than 2 inches×2 inches×6 inches. In someembodiments, the data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can be sized and shaped to fit within a box-shapedboundary having dimensions larger than 4 inches×2 inches×2 inches. Insome embodiments, the data acquisition and processing module 1020(including the imaging optics, focal plane array, and on boardprocessing electronics may) can be sized and shaped to fit within abox-shaped boundary having dimensions larger than 3 inches×3 inches×7inches. In some embodiments, the data acquisition and processing module1020 (including the imaging optics, focal plane array, and on boardprocessing electronics may) can be sized and shaped to fit within abox-shaped boundary having dimensions larger than 2 inches×1 inches×1inches. The data acquisition and processing module 1020 (including theimaging optics, focal plane array, and on board processing electronicsmay) can have dimensions less than 2 inches×2 inches×6 inches. The dataacquisition and processing module 1020 (including the imaging optics,focal plane array, and on board processing electronics may) can havedimensions greater than 1 inches×1 inches×3 inches. The data acquisitionand processing module 1020 (including the imaging optics, focal planearray, and on board processing electronics may) can have dimensionsgreater than 2 inches×2 inches×4 inches. said data acquisition andprocessing module has dimensions less than 6 inches×3 inches×3 inches.The data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canhave dimensions less than 4 inches×3 inches×3 inches. The dataacquisition and processing module 1020 (including the imaging optics,focal plane array, and on board processing electronics may) can havedimensions less than 3 inches×2 inches×2 inches. The data acquisitionand processing module 1020 (including the imaging optics, focal planearray, and on board processing electronics may) can have dimensionsgreater than 2 inches×1 inches×1 inches. The data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can have dimensions greaterthan 1 inches×0.5 inch×0.5 inch. The data acquisition and processingmodule 1020 (including the imaging optics, focal plane array, and onboard processing electronics may) can have a volume less than 30 cubicinches. The data acquisition and processing module 1020 (including theimaging optics, focal plane array, and on board processing electronicsmay) can have a volume less than 20 cubic inches. The data acquisitionand processing module 1020 (including the imaging optics, focal planearray, and on board processing electronics may) can have a volume lessthan 15 cubic inches. The data acquisition and processing module 1020(including the imaging optics, focal plane array, and on boardprocessing electronics may) can have a volume less than 10 cubic inches.The data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canhave a volume more than 1 cubic inches. The data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can have a volume more than 4cubic inches. The data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can have a volume more 5 cubic inches. The dataacquisition and processing module 1020 (including the imaging optics,focal plane array, and on board processing electronics may) can have avolume more 10 cubic inches. This package may also contain a powersupply, including a battery and/or solar module, a communicationsmodule, or both and fit into the above-referenced dimensions. It shouldbe appreciated that the dimensions disclosed herein may not correspondto the directions shown in FIG. 11A with respect to X, Y, and Z.

Moreover, the system 1000 can have a mass and weight sufficiently smallso as to enable the user 1275 to easily carry or wear the dataacquisition and processing module 1020 at the site. Thus, the embodimentshown in FIG. 11A can be sized and shaped and configured to have a massthat enables a human user to easily and effectively manipulate thesystem 1000.

FIG. 11B is a schematic diagram illustrating an installation site (e.g.an oil well site, etc.) that can be monitored by multiple infraredimaging systems 1000 (e.g., a DAISI system). For example, as shown inFIG. 11B, an imaging system 1000A can be mounted to a pole 1309 or otherstationary structure at the site. An imaging system 1000B can be worn orcarried by multiple users 1275, an imaging system 1000C can be mountedon a truck 1500, and/or an imaging system 1000D can be mounted on anaerial platform 1501, such as an unmanned aerial vehicle (UAV) or apiloted airplane. In some arrangements, the UAV can comprise anairplane, a helicopter (such as a quad helicopter), etc. The embodimentsdisclosed herein can utilize the image data captured by any combinationof the systems 1000A-1000D at the installation site to image the entireinstallation site in an efficient manner. Indeed, each installation sitecan include any suitable number and type of system 1000A-1000D. Forexample, each installation site can include greater than two systems1000A-1000D, greater than five systems 1000A-1000D, greater than tensystems 1000A-1000D, greater than twenty systems 1000A-1000D. Eachinstallation site may include less than about 100 systems 1000A-1000D.

For example, the central server can track the real-time locations ofeach imaging system 1000A-1000D based on the GPS coordinates of theparticular system or on pre-determined knowledge about the system'sstationary location. The distributed nature of the imaging systems1000A-1000D can provide rich information to the central server about thetypes and locations of gas leaks or other problems throughout multipleinstallation sites. Although FIG. 11B illustrates a stationary system1000A mounted to a fixture, a portable system 1000B to be worn orcarried by a human, a truck-based system 1000C, and an aerial-basedsystem 1000D, it should be appreciated that other types of systems maybe suitable. For example, in some embodiments, a robotic vehicle or awalking robot can be used as a platform for the systems 1000 disclosedherein. In various embodiments, a floating platform (such as a boat) canbe used as a platform for the systems 1000 disclosed herein. It shouldalso be appreciated that the systems disclosed herein can utilize anycombination of the platforms (e.g., stationary fixtures such as a pole,human user(s), truck(s) or other vehicle, aerial platform(s), floatingplatform(s), robotic platform(s), etc.) to support the systems 1000.

The systems 1000 shown in FIG. 11B can comprise a mobile DAISI system,similar to that illustrated in FIG. 11A. In other embodiments, thesystems 1000 can comprise a larger DAISI system configured for use on arelatively long-term basis. For example, the stationary imaging system1000A shown in FIG. 11B can be installed on a pole 1309 or othersuitable structure for monitoring a storage tank 1301. A solar panel1300 can be provided at or near the system 1000 to help provide power tothe system 1000. An antenna 1303 can electrically couple to the systemand can provide wireless communication between the system 1000 and anyother external entity, such as a central server, for storing and/orprocessing the data captured by the system 1000.

The stationary infrared imaging system 1000A can be programmed tocontinuously or periodically monitor the site. If a gas cloud 1302escapes from the storage tank 1301, such as by leaking from a brokenvalve, then the system 1000A can capture a multispectral, snapshot imageor series of images (e.g., a video stream) of the gas cloud 1302. Aswith the embodiment of FIG. 11A, the imaging system 1000A can includeimaging, processing, and communications components on board the system1000A to identify and characterize the types of gases in the cloud 1302and to transmit the processed data to the central server, e.g., by wayof the antenna 1303.

The imaging systems 1000B worn or carried by the multiple users 1275 canadvantageously capture and process multispectral image data of theportions of the installation site that each user 1275 visits. It shouldbe appreciated that the different users 1275 may work in or travelthrough different portions of the installation site (and also to anumber of installation sites) over a period of time. When activated, theimaging systems 1000B worn or carried by the users 1275 can continuouslyor periodically capture multispectral image data of the differentlocations at the installation site(s) to which the user 1275 travels. Asexplained herein, the system 1000B can transmit the image data and thelocation at which the image was captured to the central server. If thesystem 1000B or the central server detects a problem (such as a gasleak), then the central server can associate that leak with a particularlocation and time.

Furthermore, because the central server can receive image data andlocation data from multiple users at different locations and viewingfrom different perspectives, the central server can create anorganization-wide mapping of gas leaks that include, e.g., the locationsof gas leaks in any of multiple installation sites, the type andconcentrations and expanse or extent of each gas leaked, the particularuser 1275 that captured the image data, and the time at which the imagewas taken. Thus, each user 1275 that carries or wears a portable imagingsystem 1000B can contribute information to the central server that, whenaggregated by the central server, provides rich details on the status ofany gas leaks at any installation sites across the organization.

The truck-mounted imaging system 1000C can be mounted to a truck orother type of vehicle (such as a car, van, all-terrain vehicle, etc.).As shown in FIG. 11B, the imaging system 1000C can be connected to anend of an extendable pole or extension member mounted to the truck 1500.The system 1000C can be raised and lowered by a control system to enablethe system 1000C to image a wide area of the installation site. In someembodiments, actuators can be provided to change the angular orientationof the system 1000C, e.g., its pitch and yaw. A vibration isolation orreduction mechanism can also be provided to reduce vibrations, which maydisturb the imaging process. The system 1000C can be battery poweredand/or can be powered by the truck; in some embodiments, a generator canbe used to supply power to the system 1000C. A user can drive the truck1500 throughout the installation site to image various portions of thesite to detect leaks. In addition, the user can drive the truck 1500 toother installation sites to detect gas leaks. As explained herein, thelocation of the truck 1500 can be communicated to the central server andthe location of the truck 1500 can be associated with each capturedimage. The truck 1500 may include GPS electronics to assist in trackingthe location of the truck 1500 and/or system 1000C over time as the userdrives from place to place. Similarly, the aerial platform 1501 (such asan unmanned aerial vehicle, or UAV) can support the imaging system1000D. The aerial platform 1501 can be piloted (either remotely ornon-remotely) to numerous installation sites to capture multispectralimage data to detect gas clouds.

Thus, the systems 1000A-1000D can provide extensive data regarding theexistence of leaks at numerous installations across an organization.Monitoring numerous cameras simultaneously or concurrently across anorganization, site, region, or the entire country can be enabled atleast in part by providing wireless (or wired) communication between thesystems 1000A-1000D and one or more central servers. Advantageously, thecollection of image data from multiple sources and multiple platformscan enable the organization to create a real-time mapping of potentialgas leaks, the types and amounts of gases being leaks, the locations ofthe leaks, and the time the image data of the leak was captured. In somearrangements, the aggregation of data about a site can improve thesafety of installation sites. For example, if a gas leak is detected ata particular installation, the embodiments disclosed herein can alertthe appropriate personnel, who can begin safety and/or evacuationprocedures. Moreover, the aggregation of data across an organization(such as an oil service company) can provide site-wide, region-wide,and/or company-wide metrics for performance. For example, a givenfacility can monitor its total emissions over time and use the resultingdata to help determine the facility's overall performance. A givenregion (such as a metropolitan area, a state, etc.) can monitor trendsin emissions over time, providing a value on which to base decisions.Likewise, a company can look at the emissions performance at all of itsfacilities and can make decisions about whether some facilities shouldmake new investments to improve performance, and/or whether the entirecompany should make various improvements. The mobile systems 1000disclosed herein can thus provide a ubiquitous monitoring system fordecision making. In addition, the systems 1000 disclosed herein can beused in a feedback control process to improve various manufacturingprocedures based on the gases detected by the system(s) 1000.Accordingly, a control module may be provided to adjust themanufacturing procedure and/or parameters according to the gasesmeasured by the system 1000.

The embodiments of the mobile infrared imaging system 1000 disclosedherein provide various advantages over other systems. As explainedabove, aggregation of data about a site and its potential gas leaks canprovide an organization- or system-wide mapping of potential problems.Furthermore, automatic detection of gas leaks (and identification of thegases in the gas cloud) can simplify operation of the system 1000 andcan reduce the risk of user errors in attempting to detect or identifygas clouds manually. Moreover, the small size of the systems 1000disclosed herein are more easily carried or worn by the user than othersystems. In addition, the systems 1000 disclosed herein can overlay theidentified gas clouds on a visible image of the scene and can color codethe gas cloud according to, e.g., type of gas, concentration, etc.

FIG. 12 is a schematic system block diagram showing a mobile infraredimaging system 1000 (e.g., a mobile DAISI system), according to oneembodiment. The imaging system 1000 can include a data acquisition andprocessing module 1020 configured to be worn or carried by a person. Thedata acquisition and processing module 1020 can include, contain, orhouse an optical system 1015, a processing unit 1021, a power supply1026, a communication module 1025, and GPS module 1025. In otherembodiments, the data acquisition and processing module 1020 can beconfigured to be mounted to a structure at the site to be monitored,such as a post. The power unit 1026 can be provided on board the system1000. The power unit 1026 can be configured to provide power to thevarious system components, such as the optical system 1015, theprocessing unit 1021, the communication module 1024, and/or the GPSmodule 1025. In some embodiments, the power unit 1026 can comprise oneor more batteries (which may be rechargeable) to power the systemcomponents. In some embodiments, the power unit 1026 can include a solarpower system including one or more solar panels for powering the systemby sunlight. In some embodiments, the power unit 1026 can includevarious power electronics circuits for converting AC power supplied bystandard power transmission lines to DC power for powering the systemcomponents. Other types of power supply may be suitable for the powerunit 1026.

The system 1000 can include an optical system 1015 configured to capturemultispectral image data in a single snapshot, as explained herein. Theoptical system 1015 can correspond to any suitable type of DAISI system,such as, but not limited to, the optical systems and apparatusillustrated in FIGS. 1-10C above and/or in the optical systems 1015illustrated in FIGS. 13A-13B below. For example, the optical system 1015can include an optical focal plane array (FPA) unit and components thatdefine at least two optical channels that are spatially and spectrallydifferent from one another. The two optical channels can be positionedto transfer IR radiation incident on the optical system towards theoptical FPA. The multiple channels can be used to multiplex differentspectral images of the same scene and to image the different spectralimages on the FPA unit.

The processing unit 1021 can also be provided on board the dataacquisition and processing module 1020. The processing unit 1021 caninclude a processor 1023 and a memory 1022. The processor 1023 can be inoperable cooperation with the memory 1022, which can contain acomputer-readable code that, when loaded onto the processor 1023,enables the processor 1023 to acquire multispectral optical datarepresenting a target species of gas or chemical from IR radiationreceived at the optical FPA unit of the optical system 1015. The memory1022 can be any suitable type of memory (such as a non-transitorycomputer-readable medium) that stores data captured by the opticalsystem 1015 and/or processed by the processing unit 1021. The memory1022 can also store the software that is executed on the processor 1023.The processor 1023 can be configured to execute software instructionsthat process the multispectral image data captured by the optical system1015. For example, the processor 1023 can analyze the different imagesdetected by the FPA and can compare the captured data with knownsignatures of various types of gases or chemicals. Based on the analysisof the captured image data, the processor can be programmed to determinethe types and concentrations of gases in a gas cloud. Further, asexplained herein, the processor 1023 can analyze calibration dataprovided by the optical system 1015 to improve the accuracy of themeasurements.

Advantageously, the processor 1023 can comprise one or morefield-programmable gate arrays (FPGA) configured to execute methods usedin the analysis of the images captured by the optical system 1015. Forexample, the FPGA can include logic gates and read access memory (RAM)blocks that are designed to quickly implement the computations used todetect the types of gases in a gas cloud. The small size/weight, andhigh performance characteristics of the FPGA can enable on boardcomputation and analysis within the data acquisition and detection unit1020 worn or carried by the user. The use of FPGA (or similarelectronics) on board the system 1000 can reduce costs associated withusing an off-site central server or larger computing device to conductthe image analysis computations. In addition, enabling computation withone or more FPGA devices on board the wearable system can also preventor reduce communication bottlenecks associated with wirelesslytransmitting large amounts of raw data from the system 1000 to a remoteserver or computer, which can be used in some embodiments.

The communication module 1024 can be configured to communicate with atleast one device physically separate from the data acquisition andprocessing module 1020. For example, the communication module 1024 caninclude a wireless communication module configured to wirelesslycommunicate with the at least one separate device. The wirelesscommunication module can be configured to provide wireless communicationover wireless networks (e.g., WiFi internet networks, Bluetoothnetworks, etc.) and/or over telecommunications networks (e.g., 3Gnetworks, 4G networks, etc.).

In some embodiments, for example, the wireless communication module canprovide data communication between the data acquisition and processingmodule 1020 and a mobile device such as an electronic eyewear apparatus,a tablet computing device, a mobile smartphone, a laptop or notebookcomputer, or any other suitable mobile computing device. As explainedherein, the mobile device can include a display on which the processedimage data can be displayed to the user. For example, the types (and/orconcentrations) of gases in a gas cloud can be illustrated on thedisplay, e.g., by color coding or other suitable illustration scheme.The processed data can overlie a visible image of the scene in somearrangements. In some embodiments, the wireless communication module canprovide data communication between the system 1000 and an externaldevice remote from the system 1000, such as a central server. Forexample, the processed image data and/or the raw image data may betransmitted over a telecommunications network to the central server forstorage and/or further analysis. In some embodiments, the processed orraw image data can be uploaded to the mobile device (e.g., notebookcomputer, smartphone, tablet computing device, etc.), which can in turncommunicate the image data to the central server.

The GPS module 1025 can be configured to determine the location of thedata acquisition and processing module 1020 at a particular time. Theprocessing unit 1021 can store the location data and can associate thelocation data with a particular image captured by the optical system1015 in some arrangements. The location data associated with thecaptured images can be transmitted by the communication module 1024 (orby an external device) to a central server in some arrangements.

The optical system 1015, the processing unit 1021, the power supply1026, the communication module 1024, and/or the GPS module 1025 may becontained or housed in the data acquisition and processing module 1020,which can be carried or worn by the user. The components of the system1000 (including the optical components, the processing components, andthe communications components) may be packaged or assembled in the dataacquisition and processing module 1020 and may occupy a volume less thanabout 300 cubic inches, less than about 200 cubic inches, or less thanabout 100 cubic inches. In various embodiments, the components of thesystem 1000 (including the optical components, the processingcomponents, and the communications components) may be packaged orassembled in the data acquisition and processing module 1020 and mayoccupy a volume greater than about 2 cubic inches, or greater than about16 cubic inches. A power supply, including a battery and/or solar modulemay also be included among the components packaged or assembled in thedata acquisition and processing module 1020 and fit into theabove-referenced volumetric dimensions.

The data acquisition and processing module 1020 (with the systemcomponents mounted therein or thereon, including the imaging optics,focal plane array, and on board processing electronics may) may be sizedand shaped to fit within a box-shaped boundary having dimensions X×Y×Z.For example, in some embodiments, the data acquisition and processingmodule 1020 (including the imaging optics, focal plane array, and onboard processing electronics may) can be sized and shaped to fit withina box-shaped boundary smaller than 8 inches×6 inches×6 inches. In someembodiments, the data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can be sized and shaped to fit within a box-shapedboundary smaller than 7 inches×5 inches×5 inches. In some embodiments,the data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canbe sized and shaped to fit within a box-shaped boundary smaller than 6inches×4 inches×4 inches. In some embodiments, the data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can be sized and shaped to fitwithin a box-shaped boundary having dimensions larger than 4 inches by 2inches×2 inches. In some embodiments, the data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can be sized and shaped to fitwithin a box-shaped boundary having dimensions larger than 2 inches by 1inches×1 inches. A power supply, including a battery and/or solarmodule, a communications module, or both may be included in the dataacquisition and processing module 1020 and fit into the above-referenceddimensions. It should be appreciated that the dimensions disclosedherein may not correspond to the directions shown in FIG. 11A withrespect to X, Y, and Z. Moreover, the system 1000 can have a mass andweight sufficiently small so as to enable the user 1275 to easily carryor wear the data acquisition and processing module 1020 at the site.

FIG. 13A is a schematic system diagram of an optical system 1015configured to be used in the mobile infrared imaging systems 1000disclosed herein, according to various embodiments. As explained herein,the optical system 1015 shown in FIG. 13A can be provided in the dataacquisition and processing module 1020 to be worn or carried by theuser. The optical system 1015 can be configured to capture multispectralimage data of an object 1007, such as a gas cloud, chemical spill, etc.The components of the optical system 1015 shown in FIG. 13A may besimilar to or the same as the components of the optical systems anddevices explained herein with respect to FIGS. 1-10C. The optical system1015 can include a focal plane array (FPA) unit 1008 configured torecord infrared image data captured by the system 1000. As shown in FIG.13A, the FPA unit 1008 may advantageously be uncooled, e.g., devoid of acooling system.

The optical system 1015 can include a front window 1006 through whichlight from the object 1007 passes. A first moveable blackbody source1003 and a second moveable blackbody source 1004 can be provided toenable calibration of the optical system 1015. The moveable sources1003, 1004 can be moved in front of the field of view such that theoptics image these sources for calibration. For example, the first andsecond blackbody sources 1003, 1004 can be maintained at different knowntemperatures in a stable manner. For example, a heater and a temperaturesensor can be attached to each blackbody source 1003, 1004 to providefeedback to create a stable and known temperature difference (e.g., atleast 50 mK in some arrangements) between different spatial regions ofthe sources.

In addition, the optical system 1000 can include a dynamic calibrationapparatus to dynamically calibrate the system 1000. As shown in FIG.13A, one or more calibration sources 1009, 1010 can be provided. Thecalibration sources 1009, 1010 can comprise a thermal electricallycontrolled (TEC) material with a temperature sensor attached thereto.The calibration sources 1009, 1010 can be coated with a spectrallymeasured coating or paint. Light from the calibration sources 1009, 1010can be reflected from one or more mirrors 1005 and directed through thelens array 1002 (described below) to be imaged on a portion of the FPAunit 1008 to assist in dynamically calibrating the system 1000 (e.g.,while imaging of the target gas cloud is simultaneously being imaged).

The optical system 1000 can include a lens array 1002 to focus theincoming light onto the FPA unit 1008. As shown in FIG. 13A, each lensof the lens array 1002 can at least partially define or be included inan optical channel to be imaged by the FPA unit 1008. To improve themobility and portability of the mobile imaging system 1000, the lensarray 1002 can comprise an integrated unit formed from or assembled intoa single unitary body. Such an integrated lens array 1002 can reduce thesize of the imaging system 1015, and therefore, the size of the system1000, to at least partially enable the system 1000 to be worn or carriedby the user. The lens array 1002 can be monolithically formed in anysuitable manner. For example, in various embodiments, the lens array1002 can be formed by a diamond milling tool. In some embodiments, thelens array 1002 can comprise a monolithic piece of transparent materialwhich has separate regions shaped into curved refractive surfaces forcreating separate lenses. In some embodiments, the lenses can beinserted into an array of openings formed in a plate or substrate tocreate the lens array 1002.

The optical system 1000 can also include an array of infrared (IR)filters 1001 configured to filter wavelengths of infrared light in anappropriate manner. Examples of IR filters and filtering techniques aredisclosed herein, for example, with respect to FIGS. 5A-6D. As shown inFIG. 13A, the IR filters 1001 can be disposed between the lens array1002 and the FPA unit 1008. The IR filters 1001 can at least partiallydefine the multiple optical channels to be imaged by the FPA unit 1008.In some embodiments, the IR filters 1001 can be positioned between thelens array 1002 and the first and second moveable blackbody sources1009, 1010.

FIG. 13B is a schematic system diagram of an optical system 1015configured to be used in the mobile infrared imaging systems 1000disclosed herein, according to various embodiments. As explained herein,the optical system 1015 shown in FIG. 13B can be provided in the dataacquisition and processing module 1020 to be worn or carried by theuser. The components of the optical system 1015 shown in FIG. 13B may besimilar to or the same as the components of the optical systems anddevices explained herein with respect to FIGS. 1-10C and 13A.

The optical system 1015 of FIG. 13B can include an FPA unit 1408configured to image an object 1409, such as a gas cloud or chemicalleak. As with the embodiment illustrated in FIG. 13A, the system 1015 ofFIG. 13B can include a front window 1406 through which light from theobject 1409 passes, first and second moveable blackbody sources 1403,1404, an IR filter array 1401, and a lens array 1402. As with theembodiment of FIG. 13A, the lens array 1402 can comprise a unitary ormonolithic body. In the embodiment of FIG. 13B, the lens array 1402 maybe disposed between the filter array 1401 and the FPA unit 1408. Inother arrangements, the filter array 1401 may be disposed between thelens array 1402 and the FPA unit 1408.

The optical system 1015 of FIG. 13B can include a cooling unit 1430configured to cool the FPA unit 1408. The cooling unit 1430 can comprisea cooling finger configured to cryogenically cool the FPA array 1408 invarious arrangements. As shown in FIG. 13B, the filter array 1401, thelens array 1402, and the FPA unit 1408 can be disposed in a cooledregion 1440. The blackbody sources 1403, 1404 and front window 1406 canbe disposed in an uncooled region 1450. Disposing the blackbody sources1403, 1404 at uncooled temperatures and the filter array 1401, lensarray 1402, and FPA unit 1408 at cooled temperatures can assist in theperiodic calibration of the system 1000.

FIG. 14A is a schematic perspective view of a mobile infrared imagingsystem 1000 (e.g., mobile DAISI system) mounted to a helmet 1200,according to various embodiments. FIG. 14B is an enlarged schematicperspective view of the mobile infrared imaging system 1000 shown inFIG. 14A. The helmet 1200 can comprise a portion of a user's personalprotective equipment and can also advantageously be used as a platformfor the imaging system 1000. As explained above, the helmet 1200 can beworn by a user as the user visits a particular installation site to bemonitored, such as an oil well site, a refinery, etc. The system 1000can be activated to continuously monitor and analyze the sites that theuser visits. The system 1000 can thereby continuously and activelysearch for gas leaks wherever the user visits and can initiate an alarmor other notification if a leak is detected.

In the embodiment illustrated in FIG. 14B, the imaging system 1000 cancomprise a housing 1590, within or to which a data acquisition andprocessing module 1020 (see, e.g., FIG. 12 and associated description)is mounted or coupled. A support 1592 can be coupled to or formed withthe housing 1590 and can be configured to attach to the helmet 1200 orto any other suitable platform. For example, in some embodiments, thesupport 1592 can include one or more mounting holes for attaching to thehelmet 1200 by way of, e.g., screws, bolts, or other fasteners. Inaddition, as shown in FIG. 14B, a front window 1506 can be provided at afront end of the housing 1590. The front window 1506 can be transparentto IR radiation and can at least partially define the aperture of thesystem 1000. In some embodiments, the window 1506 comprises germanium. Adiamond like coating (DLC) or other coating or layer can be disposedover the window 1506 to provide a durable surface.

As explained herein, the system 1000 can be configured to be worn orcarried by a human user. Accordingly, the data acquisition andprocessing module 1020 can be suitably dimensioned such that a user caneasily wear or carry the system 1000. For example, the data acquisitionand processing module 1020 can be defined at least in part by dimensionsX×Y×Z, as shown in FIGS. 14A and 14B.

Unlike other systems, in which the system components are bulky or areassembled over a large form factor, the mobile system 1000 can be sizedand shaped in such a manner so as to be easily moved and manipulatedwhen the user moves about the site. Indeed, it can be very challengingto integrate the various system components in a small form-factor.Advantageously, the systems 1000 disclosed herein can be worn or carriedby a human user. For example, the components of the system 1000 can becontained together in the data acquisition and processing module 1020,which may include the housing 1590 to support the system components. Thecomponents of the system 1000 (including the optical or imagingcomponents, the focal plane array, the on-board processing electronics,and the communications components) may be packaged or assembled in thedata acquisition and processing module 1020 and may occupy a volume lessthan about 300 cubic inches, less than about 200 cubic inches, or lessthan about 100 cubic inches. In various embodiments, the components ofthe system 1000 (including the optical or imaging components, the focalplane array, the on-board processing electronics, and the communicationscomponents) may be packaged or assembled in the data acquisition andprocessing module 1020 and may occupy a volume greater than about 2cubic inches, or greater than about 16 cubic inches. In someembodiments, the components of the system 1000 (including the optical orimaging components, the focal plane array, the on-board processingelectronics, and the communications components) may be packaged orassembled in the data acquisition and processing module 1020 and mayoccupy a volume in a range of about 4 cubic inches to about 15 cubicinches. In some embodiments, the components of the system 1000(including the optical or imaging components, the focal plane array, theon-board processing electronics, and the communications components) maybe packaged or assembled in the data acquisition and processing module1020 and may occupy a volume in a range of about 5 cubic inches to about12 cubic inches. In some embodiments, the components of the system 1000(including the optical or imaging components, the focal plane array, theon-board processing electronics, and the communications components) maybe packaged or assembled in the data acquisition and processing module1020 and may occupy a volume in a range of about 4 cubic inches to about6.5 cubic inches, e.g., about 5.63 cubic inches in one embodiment. Insome embodiments, the components of the system 1000 (including theoptical or imaging components, the focal plane array, the on-boardprocessing electronics, and the communications components) may bepackaged or assembled in the data acquisition and processing module 1020and may occupy a volume in a range of about 9 cubic inches to about 13cubic inches, e.g., about 11.25 cubic inches in one embodiment. In someembodiments, the components of the system 1000 (including the optical orimaging components, the focal plane array, the on-board processingelectronics, and the communications components) may be packaged orassembled in the data acquisition and processing module 1020 and mayoccupy a volume in a range of about 6 cubic inches to about 10 cubicinches.

The data acquisition and processing module 1020 (with the systemcomponents mounted therein or thereon) may be sized and shaped to fitwithin a box-shaped boundary having dimensions X×Y×Z. For example, thedata acquisition and processing module 1020, including the imagingoptics, focal plane array, and on board processing electronics may beincluded in a package that is sized and shaped to fit within thebox-shaped boundary having dimensions X×Y×Z. This package may alsocontain a power supply, such as a battery and/or solar module. In someembodiments, the data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can be sized and shaped to fit within a box-shapedboundary smaller than 8 inches×6 inches×6 inches. In some embodiments,the data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canbe sized and shaped to fit within a box-shaped boundary smaller than 7inches×5 inches×5 inches. In some embodiments, the data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can be sized and shaped to fitwithin a box-shaped boundary smaller than 6 inches×4 inches×4 inches. Insome embodiments, the data acquisition and processing module 1020(including the imaging optics, focal plane array, and on boardprocessing electronics may) can be sized and shaped to fit within abox-shaped boundary smaller than 6 inches×2 inches×2 inches. In someembodiments, the data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can be sized and shaped to fit within a box-shapedboundary having dimensions larger than 4 inches×2 inches×2 inches. Insome embodiments, the data acquisition and processing module 1020(including the imaging optics, focal plane array, and on boardprocessing electronics may) can be sized and shaped to fit within abox-shaped boundary having dimensions larger than 2 inches×1 inches×1inches. The data acquisition and processing module 1020 (including theimaging optics, focal plane array, and on board processing electronicsmay) can have dimensions less than 3 inches×2 inches×2 inches. The dataacquisition and processing module 1020 (including the imaging optics,focal plane array, and on board processing electronics may) can havedimensions greater than 1 inches×0.5 inch×0.5 inch. The data acquisitionand processing module 1020 (including the imaging optics, focal planearray, and on board processing electronics may) can have a volume lessthan 30 cubic inches. The data acquisition and processing module 1020(including the imaging optics, focal plane array, and on boardprocessing electronics may) can have a volume less than 20 cubic inches.The data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canhave a volume less than 15 cubic inches. The data acquisition andprocessing module 1020 (including the imaging optics, focal plane array,and on board processing electronics may) can have a volume less than 10cubic inches. The data acquisition and processing module 1020 (includingthe imaging optics, focal plane array, and on board processingelectronics may) can have a volume more than 1 cubic inches. The dataacquisition and processing module 1020 (including the imaging optics,focal plane array, and on board processing electronics may) can have avolume more than 4 cubic inches. The data acquisition and processingmodule 1020 (including the imaging optics, focal plane array, and onboard processing electronics may) can have a volume more 5 cubic inches.The data acquisition and processing module 1020 (including the imagingoptics, focal plane array, and on board processing electronics may) canhave a volume more 10 cubic inches. This package may also contain apower supply, including a battery and/or solar module, a communicationsmodule, or both and fit into the above-referenced dimensions. It shouldbe appreciated that the dimensions disclosed herein may not correspondto the directions shown in FIG. 11A with respect to X, Y, and Z. Thispackage may also contain a power supply, including a battery and/orsolar module, a communications module, or both and fit into theabove-referenced dimensions. It should be appreciated that thedimensions disclosed herein may not correspond to the directions shownin FIG. 11A with respect to X, Y, and Z.

In some embodiments, the dimension X shown in FIG. 14B can be in a rangeof about 2 inches to about 7 inches, or more particularly, in a range ofabout 2 inches to about 4 inches, e.g., about 2.5 inches in oneembodiment. In some embodiments, the dimension X shown in FIG. 14B canbe in a range of about 4 inches to about 6 inches, e.g., about 5 inchesin one embodiment. In some embodiments, the dimension Y shown in FIG.14B can be in a range of about 1 inch to about 5 inches, or moreparticularly, in a range of about 1 inch to about 3 inches, e.g., about1.5 inches in one embodiment. In some embodiments, the dimension Z shownin FIG. 14B can be in a range of about 1 inch to about 5 inches, or moreparticularly, in a range of about 1 inch to about 3 inches, e.g., about1.5 inches in one embodiment.

Moreover, the system 1000 can have a mass and weight sufficiently smallso as to enable the user 1275 to easily carry or wear the dataacquisition and processing module 1020 at the site. For example, thesystem 1000 can have a weight in a range of about 0.5 pounds to 5pounds, or more particularly, in a range of about 0.5 pounds to 2pounds, or more particularly in a range of about 0.25 pounds to about 2pounds, or more particularly, in a range of about 0.25 pounds to about1.5 pounds. In one embodiment, for example, the system 1000 can weightabout 1 pound. In another embodiment, for example, the system 1000 canweigh about 0.5 pounds. Thus, the embodiment shown in FIG. 11A can besized and shaped and configured to have a mass that enables a human userto easily and effectively manipulate the system 1000.

FIG. 14C is a perspective cross-sectional view of the mobile infraredimaging system 1000 shown in FIGS. 14A-14B. The mobile infrared imagingsystem 1000 can include one or more movable shutters 1503 (e.g., twoshutters) rear of the window 1506 and a lens assembly 1502 rear of theshutter(s) 1503. A filter array 1501 can be disposed rear (or forward)of the second lens array 1502B, and an optical focal plane array (FPA)unit 1508 can be disposed rear of the filter array 1501. The optical FPAunit 1508 can be mechanically and electrically coupled with one or moresubstrates 1586, which may comprise printed circuit board or PCBsubstrates. In various embodiments, the FPA unit 1508 comprises a singleFPA or detector array. Additionally, as explained herein, the lensassembly 1502, filter array 1501, and optical FPA unit can at leastpartially define one or more optical channels that are spatially andspectrally different. A number of the optical channels can be at least4, at least 5, at least 8, at least 9, at least 12, at least 13, or atleast 20. In some embodiments, a number of the optical channels isbetween 4 and 50.

One or more batteries 1588 can supply power to the system 1000 by way ofthe substrate(s) 1586. In addition, a visible light imaging sensor 1580can be disposed in the housing 1590 and can be configured to provide avisible light image of the scene being captured by the system 1000. Theprocessed IR image data can be overlaid upon the visible light image. Invarious embodiments the visible light imaging sensor 1580 can be usedfor reduction of scene-motion-induced detection errors, for example, todetect a moving object that enters the field of view (such as an animalor person) and would interfere with the data being collected.

As explained herein, the movable shutter(s) 1503 can be configured toprovide spectral-radiometric calibration for the system 1000. Theshutter(s) 1503 can be configured to move in and out of the field ofview of the lens assembly 1502 periodically, e.g., in a time period in arange of about 1 minute to about 15 minutes, or more particularly, in arange of about 3 minutes to about 7 minutes, e.g., about 5 minutes.Although one shutter 1503 is illustrated in FIG. 14C, it should beappreciated that two or more shutters may be provided. The shutter(s)1503 can be used in static calibration procedures to provide the systemwith absolute temperature values. In some embodiments, only staticcalibration is performed, e.g., no dynamic calibration is performed. Insome embodiments, both static and dynamic calibration procedures areperformed.

The lens assembly 1502 can include a first lens array 1502A and a secondlens array 1502B. In some embodiments, the lens assembly 1502 cancomprise an array of two-part lenses denoted by the first and secondarrays 1502A, 1502B. In some embodiments, the lens assembly 1502 cancomprise an array of two separate lenses denoted by the first and secondarrays 1502A, 1502B. Each of the lens arrays 1502A, 1502B can comprise a4×3 array of lenses, each of which may correspond to a particulardetector region in the FPA unit 1508 and can define an optical channelof the system 1000. The lenses used in the first lens array 1502A may bedifferent from the lenses used in the second lens array 1502B. Thelenses can be any suitable type of lens, including, e.g., sphericallenses, aspheric lenses, rod lenses, etc. or any combination thereof.For example, the lenses used in the first lens array 1502A can compriseaspheric lenses, and the lenses used in the second lens array 1502B cancomprise rod lenses. Although the lens assembly 1502 shown in FIG. 15Cincludes two lens arrays, it should be appreciated that additional lensarrays may be used, e.g., three lens arrays, four lens arrays, five lensarrays, etc. In addition, to assist in enabling a small system size, thediameter of each lens in the assembly 1502 can be less than about 0.5″,e.g., in a range of about 0.1″ to about 0.5″. The f-number of each lenscan be less than about 2, e.g., in a range of about 0.2 to 2, or moreparticularly, in a range of about 0.5 to 2, or 1.0 to 2 or 1.1 to 2.

The first lens array 1502A and the second lens array 1502B can becoupled to one another by way of a mounting plate 1584 sized and shapedto support or receive each lens array 1502A, 1502B. For example, thefirst lens array 1502A can be mounted on one side of the mounting plate1584, and the second lens array 1502B can be mounted on an opposite sideof the mounting plate 1584. The mounting plate 1584 can be machined tohave diameter tolerances of about +/−25 microns. The lenses of thearrays 1502A, 1502B can be secured to the mounting plate 1584 with acurable epoxy. For example, the lenses may fit into opposite sides ofholes formed in the mounting plate 1584.

The optical FPA unit 1508 can comprise any suitable type of detectorarray that is configured to detect infrared radiation, for example,greater than 1 micron, or greater than 2 microns, or greater than 3microns or greater than 5 microns, or greater than 6 microns andpossibly lower than 20 microns, or 15 microns, or 13 microns, or 12microns or 10 microns, in wavelength, and may be cooled or uncooled. Insome embodiments the optical FPA unit 1508 comprises one or moremicrobolometer arrays, which may be uncooled. For example, an array ofabout 1000×1000 microbolometer arrays may be used in the embodimentsdisclosed herein. Microbolometer arrays such as those manufactured byDRS Technologies of Arlington, Va., and Sofradir EC, Inc., of Fairfield,N.J., may be suitable for the embodiments disclosed herein. For example,the DRS U8000 FPA manufactured by DRS Technologies may be used in someembodiments. In some arrangements, the microbolometer array may have aresolution of 1024×768 with a pixel pitch of 12 microns. The array oflenses can form separate channels having image detection regions thatform part of the array. For example, 12 channels can be included in the1024×768 pixel array with on the detector array (microbolometer array)that are for example 250×250 pixels for each of the 12 channels.Detector arrays having more or less pixels may be employed. Similarlythe number of channels be larger or smaller than 12 and the detectionare on the detector array for a single channel may be larger or smallerthan 250×250 pixels. For example, the detection region may comprise frombetween 100-200 pixels×100-200 pixels per detection region, For example,the detection region may comprise from between 100-200 pixels×100-200pixels per detection region, from between 200-300 pixels×200-300 pixelsper detection region, or from between 300-400 pixels×300-400 pixels orfrom between 400-500 pixels×400-500 pixels. Likewise the detectionregion for a channel may measure 100-200 pixels on a side, 200-300pixels on a side, 300-400 pixels on a side, 400-500 pixels on side orlarger or smaller. In some arrangements, the spectral band of themicrobolometer can be about 7.5 microns to 14 microns. Themicrobolometer array can operate at a frame rate of about 30 Hz and canoperate at operating temperatures of about −40° C. to +70° C. In variousembodiments, the microbolometer array is an uncooled microbolometer thatdoes not include a cooler. The sensitivity of the microbolometer at F/1can be <about 40 mK. The systems 1000 disclosed herein can be used todetect wavelengths in a range of about 1 micron to about 20 microns. Forexample, the systems 1000 disclosed herein can be used to detectwavelengths above about 6 microns, e.g., in a range of about 6 micronsto about 18 microns, or more particularly, in a range of about 7 micronsto about 14 microns. In various embodiments, the individual detectorelements of the microbolometer array can be spaced relatively closetogether to at least partially enable a small, compact system. Forexample, adjacent detector elements of the array can be spaced apart bya distance in a range of about 7 microns to about 15 microns, or moreparticularly in a range of about 9 microns to about 13 microns, e.g.,about 11 microns. The individual lenses can be spaced apart by adistance in a range of about 20 mm to about 35 mm, e.g. in a range ofabout 24 mm to about 30 mm, e.g., about 27.5 mm. Likewise the spatiallyand spectrally spaced channels may be physically spaced apart by 20 to35 mm, 24 mm to 30 mm, etc. Although various embodiments of the systemare described as including an FPA comprising for example amircobolometer array, certain embodiments comprise a plurality of FPAs.In some embodiments, a single optical FPA is used. In some embodiments,detectors of the optical FPA are configured to detect radiation in thesame band of IR wavelengths.

The on-board processing electronics of the data acquisition andprocessing module 1020 can process the IR optical data to detect and/oridentify a target species from the IR radiation received at the opticalFPA. For example, the module 1020 can be configured to acquiremultispectral image data and analyze the acquired image data to identifythe target species. For example, the mobile imaging systems 1000disclosed herein can be configured to image a 10 m×10 m object area at adistance of about 17 m at a resolution of about 0.04 m. In this example,any gas leaks that generate a gas cloud of at least about 1.5 inches insize can be detected and/or identified by the system 1000. The detectionand identification methods can be performed substantially in real-timesuch that the user can be alerted if any leaks are identified.

As explained above, the infrared image data captured by the system 1000can be processed on board the data acquisition and processing module1020 of the imaging system 1000. One way to provide a smaller system1000 is to process the image data using one or more field-programmablegate arrays (FPGA) configured to execute methods used in the analysis ofthe images captured by the optical system 1015. In some embodiments, oneor more Application Specific Integrated Circuits (ASICs) may be usedinstead of, or in addition to, the FPGAs. For example, an ASICs chip mayinclude an FPGA. The FPGA(s) (and/or ASIC(s)) can be mounted to andelectrically coupled with the substrate(s) 1586 shown in FIG. 14C andcan be physically located proximate the optical system. For example, theFPGA can include logic gates and read access memory (RAM) blocks thatare designed to quickly implement the computations used to detect thetypes of gases in a gas cloud. The small size/weight, and highperformance characteristics of the FPGA can enable on board computationand analysis within the data acquisition and detection unit 1020 worn orcarried by the user. The use of FPGA (or similar electronics) on boardthe system 1000 can reduce costs associated with using an off-sitecentral server or larger computing device to conduct the image analysiscomputations. Advantageously, the embodiments disclosed herein canenable on-board computation even though it can be challenging toimplement complex methods on the limited computing platform that FPGAsprovide.

In addition, enabling computation with one or more FPGA devices on boardthe wearable system can also prevent or reduce communication bottlenecksassociated with wirelessly transmitting large amounts of raw data fromthe system 1000 to a remote server or computer. For example, theinfrared optical system 1015 disclosed herein may generate up to about380 Mbps of raw image data at 30 frames per second, and the visiblesensor 1580 may generate about 425 Mbps of raw image data at 30 framesper second. The resulting data rate of about 800 Mbps is faster thanmost conventional wireless technologies. While data compression and/orpre-processing may reduce the raw data rates for the visible and IRimages, in some embodiments, the IR image data may only be compressed bya ratio of about 2:1. The resulting overall data rate of about 192 Mbpsmay not be transmitted effectively by conventional wirelesscommunications devices. Accordingly, performing the image processingcalculations on board the system 1000 (e.g., on the data acquisition andprocessing module 1020) can reduce the occurrence of or avoidbottlenecks generated by wirelessly communicating the raw image data toan off-site central server.

One challenge to implementing a mobile imaging system is the powerrequirements of each component of the system, including, e.g., the IRoptical system 1015, the visible sensor 1580, the processingelectronics, the wireless communications modules, etc. Advantageously,the mobile infrared imaging systems 1000 disclosed herein can beconfigured to operate by battery power for long periods of time withoutrecharging or replacing the batteries 1588. In some arrangements the oneor more batteries 1588 can comprise lithium ion batteries, which haverelatively high energy densities. In addition, to help reduce powerconsumption within the system 1000, the FPGAs of the data acquisitionand processing module 1020 can be advantageously programmed such thatpower consumption is lower than that used for other types of processingelectronics.

The systems 1000 disclosed herein can advantageously operate for between8 hours and 36 hours without recharging or replacing the batteries, ormore particularly between about 10 hours and 24 hours without rechargingor replacing the batteries. In some embodiments, the system 1000 canoperate for at least about 12 hours without recharging or replacing thebatteries. The components of the data acquisition and processing module1020 (including the imaging optics, focal plane array, and on boardprocessing electronics may) can be configured to operate at relativelylow electrical power levels, e.g., at power levels in a range of about 3W to about 10 W, or more particularly in a range of about 4 W to about 7W, or in a range of about 4 W to about 6 W, e.g., about 5 W in someembodiments. The components of the data acquisition and processingmodule 1020 (including the imaging optics, focal plane array, and onboard processing electronics may) can also be configured to operate atrelatively low overall energy levels for a single charge of thebatteries 1588, e.g., at energy levels in a range of about 60 Watt-hours(Wh) to about 100 Wh, or more particularly in a range of about 80 Wh toabout 95 Wh, or in a range of about 85 Wh to about 90 Wh.

In addition, for each of the embodiments disclosed herein, variousmotion detection and/or compensation techniques can be implemented toaccount for relatively large-scale motions that are induced by the usermoving his or her head during use. For example, when a user is visitinga well site or other installation, the user may be continuously walkingand looking in different directions (e.g., by rotating his or her head).Additionally, vibration can be introduced by the user's naturalunsteadiness. Such movement can continuously change the system's fieldof view at a relatively rapid rate, which can affect the accuracy of themethods used to determine the identity of species in a gas cloud orother object. Accordingly, it can be desirable to provide improvedmotion detection and/or compensation techniques to reduce errorsassociated with the movements of the user.

Each of the embodiments disclosed herein can be used to estimate variouscharacteristics of gases present in a gas leak imaged by the infraredimaging systems disclosed herein.

References throughout this specification to “one embodiment,” “anembodiment,” “a related embodiment,” or similar language mean that aparticular feature, structure, or characteristic described in connectionwith the referred to “embodiment” is included in at least one embodimentof the present invention. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” and similar language throughout thisspecification may, but do not necessarily, all refer to the sameembodiment. It is to be understood that no portion of disclosure, takenon its own and in possible connection with a figure, is intended toprovide a complete description of all features of the invention.

In the drawings like numbers are used to represent the same or similarelements wherever possible. The depicted structural elements aregenerally not to scale, and certain components are enlarged relative tothe other components for purposes of emphasis and understanding. It isto be understood that no single drawing is intended to support acomplete description of all features of the invention. In other words, agiven drawing is generally descriptive of only some, and generally notall, features of the invention. A given drawing and an associatedportion of the disclosure containing a description referencing suchdrawing do not, generally, contain all elements of a particular view orall features that can be presented is this view, for purposes ofsimplifying the given drawing and discussion, and to direct thediscussion to particular elements that are featured in this drawing. Askilled artisan will recognize that the invention may possibly bepracticed without one or more of the specific features, elements,components, structures, details, or characteristics, or with the use ofother methods, components, materials, and so forth. Therefore, althougha particular detail of an embodiment of the invention may not benecessarily shown in each and every drawing describing such embodiment,the presence of this detail in the drawing may be implied unless thecontext of the description requires otherwise. In other instances, wellknown structures, details, materials, or operations may be not shown ina given drawing or described in detail to avoid obscuring aspects of anembodiment of the invention that are being discussed. Furthermore, thedescribed single features, structures, or characteristics of theinvention may be combined in any suitable manner in one or more furtherembodiments.

Moreover, if the schematic flow chart diagram is included, it isgenerally set forth as a logical flow-chart diagram. As such, thedepicted order and labeled steps of the logical flow are indicative ofone embodiment of the presented method. Other steps and methods may beconceived that are equivalent in function, logic, or effect to one ormore steps, or portions thereof, of the illustrated method.Additionally, the format and symbols employed are provided to explainthe logical steps of the method and are understood not to limit thescope of the method. Although various arrow types and line types may beemployed in the flow-chart diagrams, they are understood not to limitthe scope of the corresponding method. Indeed, some arrows or otherconnectors may be used to indicate only the logical flow of the method.For instance, an arrow may indicate a waiting or monitoring period ofunspecified duration between enumerated steps of the depicted method.Without loss of generality, the order in which processing steps orparticular methods occur may or may not strictly adhere to the order ofthe corresponding steps shown.

The features recited in claims appended to this disclosure are intendedto be assessed in light of the disclosure as a whole.

At least some elements of a device of the invention can becontrolled—and at least some steps of a method of the invention can beeffectuated, in operation—with a programmable processor governed byinstructions stored in a memory. The memory may be random access memory(RAM), read-only memory (ROM), flash memory or any other memory, orcombination thereof, suitable for storing control software or otherinstructions and data. Those skilled in the art should also readilyappreciate that instructions or programs defining the functions of thepresent invention may be delivered to a processor in many forms,including, but not limited to, information permanently stored onnon-writable storage media (e.g. read-only memory devices within acomputer, such as ROM, or devices readable by a computer I/O attachment,such as CD-ROM or DVD disks), information alterably stored on writablestorage media (e.g. floppy disks, removable flash memory and harddrives) or information conveyed to a computer through communicationmedia, including wired or wireless computer networks. In addition, whilethe invention may be embodied in software, the functions necessary toimplement the invention may optionally or alternatively be embodied inpart or in whole using firmware and/or hardware components, such ascombinatorial logic, Application Specific Integrated Circuits (ASICs),Field-Programmable Gate Arrays (FPGAs) or other hardware or somecombination of hardware, software and/or firmware components.

While examples of embodiments of the system and method of the inventionhave been discussed in reference to the gas-cloud detection, monitoring,and quantification (including but not limited to greenhouse gases suchas Carbon Dioxide, Carbon Monoxide, Nitrogen Oxide as well ashydrocarbon gases such as Methane, Ethane, Propane, n-Butane,iso-Butane, n-Pentane, iso-Pentane, neo-Pentane, Hydrogen Sulfide,Sulfur Hexafluoride, Ammonia, Benzene, p- and m-Xylene, Vinyl chloride,Toluene, Propylene oxide, Propylene, Methanol, Hydrazine, Ethanol,1,2-dichloroethane, 1,1-dichloroethane, Dichlorobenzene, Chlorobenzene,to name just a few), embodiments of the invention can be readily adaptedfor other chemical detection applications. For example, detection ofliquid and solid chemical spills, biological weapons, tracking targetsbased on their chemical composition, identification of satellites andspace debris, ophthalmological imaging, microscopy and cellular imaging,endoscopy, mold detection, fire and flame detection, and pesticidedetection are within the scope of the invention.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. The steps of a method or algorithm disclosedherein may be implemented in a processor-executable software modulewhich may reside on a computer-readable medium. Computer-readable mediaincludes both computer storage media and communication media includingany medium that can be enabled to transfer a computer program from oneplace to another. A storage media may be any available media that may beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media may include RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that may be used to store desired programcode in the form of instructions or data structures and that may beaccessed by a computer. Also, any connection can be properly termed acomputer-readable medium. Disk and disc, as used herein, includescompact disc (CD), laser disc, optical disc, digital versatile disc(DVD), floppy disk, and blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above also may be included within the scope ofcomputer-readable media. Additionally, the operations of a method oralgorithm may reside as one or any combination or set of codes andinstructions on a machine readable medium and computer-readable medium,which may be incorporated into a computer program product.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

1. (canceled)
 2. A method for monitoring the presence of one or more target gases, the method comprising: receiving image data from a plurality of IR imaging systems, each IR imaging system configured to capture infrared images of the one or more target gases in real-time and to associate each captured infrared image with a location at which the one or more target gases are present; and processing the received image data to identify the location at which the one or more target gases is detected.
 3. The method of claim 2, further comprising mapping, within the one or more installation sites, the location at which the one or more target gases is detected.
 4. The method of claim 2, further comprising mapping, within the one or more installation sites, the location at which the or more target gases is detected, a type of target gas detected and a concentration of the type of target gas detected.
 5. The method of claim 2, further comprising detecting the presence of the one or more target gases based on the image data received from the plurality of IR imaging systems.
 6. The method of claim 2, further comprising receiving pre-processed image data from the plurality of IR imaging systems, the pre-processed image data comprising data associated with the presence of the one or more target gases.
 7. The method of claim 2, wherein the plurality of IR imaging systems are worn or carried by a plurality of persons.
 8. The method of claim 2, further comprising receiving IR image data from a plurality of truck-based IR imaging systems, each truck-based IR imaging system configured to be mounted to a truck and configured to capture infrared images of the one or more target gases in real-time.
 9. The method of claim 2, further comprising receiving IR image data from a plurality of aerial-based IR imaging systems, each aerial-based IR imaging system configured to be mounted to an aerial platform and configured to capture infrared images of the one or more target gases in real-time.
 10. The method of claim 2, further comprises receiving IR image data from a plurality of imaging systems mounted to stationary structures at the one or more installation sites.
 11. The method of claim 2, wherein each IR imaging system of the plurality of IR imaging systems comprises a plurality of spectrally and spatially distinct optical channels, wherein receiving the image data comprises receiving multi-spectral image data from the plurality of spectrally and spatially distinct optical channels of each IR imaging system of the plurality of IR imaging systems.
 12. The method of claim 11, wherein processing the received image data comprises processing the multi-spectral image data to identify the location at which the one or more target gases is detected.
 13. A non-transitory computer-readable medium having a program stored thereon, the program comprising instructions for implementing the method according to claim 2, when these instructions are executed by a process.
 14. A server for monitoring the presence of one or more target gases at one or more installation sites, the system comprising: a communications module configured to receive image data from a plurality of IR imaging systems, each IR imaging system configured to capture infrared images of the one or more target gases in real-time and to associate each captured infrared image with a location at which the one or more target gases are present; and processing circuitry including a processor configured to process the received image data to identify the location at which one or more target gases is detected.
 15. The server of claim 14, wherein the processor is further configured to map the location, within the one or more installation sites, at which the one or more target gases is detected.
 16. The server of claim 14, wherein the processor is further configured to identify a type of target gas detected based on the received image data.
 17. The server of claim 14, wherein the communications module is further configured to receive data identifying a type of target gas detected by one or more of the IR imaging systems.
 18. The server of claim 14, wherein the processor is further configured to identify a concentration of target gas based on the received image data.
 19. The server of claim 14, wherein the communications module is further configured to receive data identifying a concentration of target gas detected by one or more of the IR imaging systems.
 20. The server of claim 14, wherein each IR imaging system of the plurality of IR imaging systems comprises a plurality of spectrally and spatially distinct optical channels, and wherein the communications module is configured to receive multi-spectral image data from the plurality of spectrally and spatially distinct optical channels of each IR imaging system of the plurality of IR imaging systems.
 21. The server of claim 20, wherein the processor is configured to process the multi-spectral image data to identify the location at which one or more target gases is detected. 